IAEA - Radiation Protection for LINACs

7/25/2019 IAEA - Radiation Protection for LINACs

1/342

T E C H N I C A L R E P O R T S S E R I E S N o .

188

Radiological Safety Aspects

of the O peration of

Electron Linear Accelerators

i

1

1

I N T E R N A T I O N A L A T O M I C E N E R G Y A G E N C Y , V I E N N A , 1 9 7 9

j y


2/342

RADIOLOGICAL S AFETY AS PECTS

OF TH E OPERATION OF

ELECTRON LINEAR ACCELERATORS


3/342

The fo l lowing Sta tes a re Members of the In te rna t iona l Atomic Energy Agency:

A F G H A N I S T A N

A L B A N I A

A L G E R I A

A R G E N T I N A

A U S T R A L I A

A U S T R I A

B A N G L A D E S H

B ELG IU M

B O LIV IA

B R A Z I L

B U L G A R I A

B U R M A

B Y E L O R U S S I A N S O V I E T

SO C IA LIST R EPU B LIC

C A N A D A

C H I L E

C O L O M B I A

C O STA R IC A

CUBA

C Y P R U S

C Z E C H O S L O V A K I A

D E M O C R A T I C K A M P U C H E A

D E M O C R A T I C P E O P L E ' S

R E P U B L I C O F K O R E A

D E N M A R K

D O MIN IC A N R EPU B LIC

E C U A D O R

E G Y P T

E L S A L V A D O R

E T H I O P I A

F I N L A N D

F R A N C E

G A B O N

G E R M A N D E M O C R A T I C R E P U B L I C

G E R M A N Y , F E D E R A L R E P U B L I C O F

G H A N A

G R E E C E

G U A T E M A L A

HAITI

H O LY SEE

H U N G A R Y

I C E L A N D

IN D IA

I N D O N E S I A

IR A N

I R A Q

I R E L A N D

I S R A E L

I T A L Y

I V O R Y C O A S T

J A M A I C A

J A P A N

J O R D A N

K E N Y A

K O R E A , R E P U B L I C O F

K U W A IT

L E B A N O N

L I B E R I A

L I B Y A N A R A B J A M A H I R I Y A

L I E C H T E N S T E I N

L U X E M B O U R G

M A D A G A S C A R

M A L A Y S I A

MALI

M A U R I T I U S

MEX IC O

M O N A C O

M O N G O L I A

M O R O C C O

N E T H E R L A N D S

N E W Z E A L A N D

N I C A R A G U A

N I G E R

N I G E R I A

N O R W A Y

P A K I S T A N

P A N A M A

P A R A G U A Y

P E R U

P H I L I P P I N E S

P O L A N D

P O R T U G A L

Q A T A R

R O M A N I A

SA U D I A R A B IA

S E N E G A L

S I E R R A L E O N E

S I N G A P O R E

S O U T H A F R I C A

SPAIN

SR I LA N K A

S U D A N

SW ED EN

S W I T Z E R L A N D

S Y R I A N A R A B R E P U B L I C

T H A I L A N D

T U N I S I A

T U R K E Y

U G A N D A

U K R A I N I A N S O V I E T S O C I A L I S T

R EPU B LIC

U N I O N O F S O V I E T S O C I A L I S T

R E P U B L I C S

U N I T E D A R A B E M I R A T E S

U N I T E D K I N G D O M O F G R E A T

B R I T A I N A N D N O R T H E R N

I R E L A N D

U N I T E D R E P U B L I C O F

C A M E R O O N

U N I T E D R E P U B L I C O F

T A N Z A N I A

U N I T E D S T A T E S O F A M E R I C A

U R U G U A Y

V E N E Z U E L A

V IET N A M

Y U G O S L A V I A

Z A I R E

ZA MB IA

The Agenc y 's Sta tu te was appro ved on 23 Oc tobe r 1956 by the Con feren ce on the Sta t u te of the IAEA

held a t Uni ted Na t ions Head quar te rs , New Yor k; i t en te r ed in to forc e on 29 July 1957. Th e Hea dqu arte rs of

the Agency a re s i tua te d in Vienna . I t s pr inc ipa l objec t ive is " to acce le ra te and enla rge the con tr ib ut io n of

a tomic energy to peace , hea l th and prosper i ty throughout the world" .

IA EA , 1979

Permission to reprod uce o r t ransla te the info rm at io n con ta ine d in th is publ ica t ion may be obta ined by

wri t ing to the In te rna t i ona l At om ic Energy A gency, KSr ntner Ring 11, P .O. Box 590, A-10 11 Vienna , Austr ia .

Pr in ted by the IAEA in Austr ia

Fe b rua ry 1979


4/342

TECHN ICAL REPOR TS S ERIES No . 1 8 8

RADIOLOGICAL SAFETY ASPECTS

OF THE OPERATION OF


A manual w r i t ten by

William P. SWANSON

Stanford Linear Accelerator Center

Stanford University

United States of America

Wo rk supported in part by the

United States Departm ent of Energy

INTERNATIONAL ATOMIC ENERGY AGENCY

VIENNA, 1979


5/342

RADIOLOGICAL SAFETY ASPECTS

O F TH E O PERA TIO N O F

ELECTRO N LIN EA R A CCELERA TO RS

IAEA, VIENNA, 1979

STI /D O C/ lO /188

I S B N 9 2 - 0 - 1 2 5 1 7 9 - 3


6/342

F O R E W O R D

Electron l inear accelerators are being used throughout the world in

increasing num bers in a var iety of im por tan t applicat ions. Fo rem ost am ong

these is their role in the treatment of cancer with both photon and electron

rad iatio ns in the energy range 440 MeV. To a greater ex ten t linear accelera-

tors are replacing

6 0

Co sources and betat ron s in medical applicat ions. Com-

mercial uses include non-destructive test ing by radiography, foo d preservation,

product sterilization and radiation processing of materials such as plastics and

adhesives. Scie ntific app licatio ns include investigations in radia tion biology ,

radiat ion chemistry, nuclear and elementary-part icle physics and radiat ion

research.

This manual is conceived as a source book providing authori tat ive

guidance in radiat ion protect ion from an important category of radiat ion

sources. I t thus supp leme nts othe r ma nuals of the Agency related to the

planning and imp lem entat io n of radiat ion prote ct ion programm es. The

author , W.P. Swanson of Stanford Linear Accelerator Center , USA, was

engaged as a consultant by the Agency to compile and write the manual,

and the Agency wishes to express its gratitude to him.

A dr af t was sent to a num ber of experts in var ious countr ies. The

Agency gratefully acknowledges the helpful comments, which have been

taken into account in the f inal text , f rom J. Rassow, K. Tesch (Federal

Republic of Germany), M. Ladu (I taly) , T. Nakamura (Japan) , G.R. Higson

(United Kingdom), F.H. Att ix , R.C. McCall and C.S. Nunan (United States

of America) . The Agency 's off icer responsible for this proje ct was F.N . Flakus

of the Radiological Safe ty Sectio n, Division of Nu clear Safe ty and Environ-

menta l Pro tec t ion .

Comments f rom readers for possible inclusion in a later edit ion of the

ma nua l wou ld be we lcom e; they should be addressed to the D irector, Division

of Nuclear Safety and Environmental Protect ion, International Atomic

Energy Agency, Karntner Ring 11, P.O. Box 590, A-1011 Vienna, Austria.


7/342


8/342

CONTENTS

INTRODUCTION 1

Pu rpose and scope of th e M anual 2

Terminology and units 5

Acknowledgements 5

1. USES AN D CHA RACT ERISTICS OF ELECTRO N LINEA R

A C C E L E R A T O R S 7

1.1. Fields of app lication 7

1.2. Typ es of electro n linear accelerato r installatio ns 8

1.3. Para me ters of electron linear accelerato rs 11

2 . RADIATIONS AT ELECTRON LINEAR ACCELER ATOR

INSTALLATIONS 27

2.1. R adiat ions anticipated and their quali ty facto rs 27

2.1.1. Ty pes of radia tions and their sources 27

2.1.2. Quali ty facto rs 29

2.2. Ph oto n diffe ren tial track length and estim ation of yields . .. . 34

2.3. Electron beam s 43

2.4. Ph oton s 50

2.4.1. Extern al brems strahlung 50

2.4.2. Scattered ph oto ns 57

2.5. Ne utrons 61

2.5.1. Ne utron quali ty facto r and dose equivalent 61

2.5.2. Prod uctio n mechan isms 65

2.5.3. Ne utron yields fro m electron beam s 79

2.5.3.1. The giant-resonance region (E

0

< 35 MeV ) . 82

2 .5.3 .2 . Neu t ron p roduc t ion fo r 3 4 < E

0

< 150M eV. 88

2.5.3.3. N eutro n prod uction for E

0

> 150 MeV .... 91

2.6. Radioactivi ty induced in com pon ents 97

2.6.1. Installa tions with E

0

< 3 5 MeV 101

2.6.2. Activity induc ed by high-energy beam s 101

2.7. Activity induc ed in air and wate r 126

2.7.1. Airborne radioactivi ty 126

2.7.1.1 . Air activa tion 126

2.7.1 .2. Dust 131

2.7.2. Activity induc ed in wa ter 136


9/342

2.8. M uons 142

2.9. Cha rged-p article secondary beam s 147

2.10. Pr od uct ion of tox ic gases 149

2.10.1. Co ncen trat ion buildup and removal 151

2.10.2. Produ ction rates 152

2.11. X-rays generated by microwave system s 156

2.11 .1. Oscillators and am plifiers 156

2.11.2 . Microwave cavities 158

3 . RAD IATION SHIELDING 160

3.1. Ty pes of areas and shielding criteria 160

3.1.1. Acce lerator scheduling and workload facto r

W

160

3.1.2. Prim ary and second ary barriers and the

orienta t ion (use) fac tor U 162

3.1.3. Occu pancy facto r T 164

3.2. Shielding ma terials 165

3.3. Physical cons ideratio ns 168

3.4. Shielding against ph ot on s 175

3.4.1. Primary barriers (E

0

< 100 MeV ) 175

3.4.2. Secondary barr iers ( E

0

< 100 MeV ) 177

3.4.3. Ac celerato rs opera ting above 100 MeV 186

3.5. Shielding against ne utr on s 189

3.5.1. Energies below the pho topio n threshold

(E

0

< 140 MeV) 190

3.5.2. High-energy installations ( E

0

> 140 MeV ) 197

3.6. Laby rinths, doors, voids and pen etrat io ns 199

4 . TYPICAL INSTAL LATION S 205

4.1. Medical installa tions 205

4.2. Industr ial radiographic instal lations 207

4.3. Rese arch and special-purpose installation s 21 4

5 . RADIATION MON ITORING AND INTERPRE TATION OF

MEASUREMENTS 226

5.1. Character ist ics and choice of mo nitor ing equip m ent 22 6

5.2. Du ty fact or effe cts on radiat ion me asurem ents 236

5.2.1. Dead-t ime effec ts in pulse coun ters 237

5.2.2. Rec om bination in ionizat ion cham bers 238


10/342

5.3 . Neu tron mon i tor ing techniques 242

5 .3 .1 . Fluence measurem ents 243

5.3.2. Spectral me asurem ents 252

5.4. Rad iat ion surveys 255

5.5. Instr um ent cal ibrat ion and ma intenan ce 260

6 . R E Q U I R E M E N T S F O R A N E F F E C T I V E S A F E T Y P R O G R A M M E . . 2 6 3

6.1. Safety organizat ion 26 3

6 .2 . Safe ty program me 263

6.3. Rad iat ion safety 265

6.4. Acc elerator safety 268

6.5. Linear accelerators used in radiat ion therapy 270

6.5.1. General radiat ion safety 271

6.5.2. Reliabili ty of dosim etry 272

6.5.3. Co ntrol of dose distr ibution 273

6.5.4. Safe del ivery of the prescr ibed trea tm en t 27 4

6.5.5. Provisions to facilita te acc urate pat ien t pos itionin g . .. . 27 6

6.5.6. Co ntrol of unw ante d dose to pat ien t 277

6.5.7. Pro tect io n against othe r r isks 279

6.6. Sa fety at indu strial and research installatio ns 28 2

7 . GEN ERA L BIBLIOGRAPH Y 286

APPENDIXES 293

Ap pend ix A. Physical and num erical cons tants 294

Ap pend ix B. Rad iat ion param eters of mater ials 297

Ap pend ix C. Rules of th um b 318

Ap pendix D. Addresses of organizat ions 322


11/342


12/342

INTRODUCTION

More than a decade of experience has been gained since the publication of

a manual devoted exclusively to radiological protection at high-energy electron

acc elerato rs. Because of the rapidly increasing use of elec tron linear accele rators,

i t was felt th at i t would be usefu l to prepare such a ha nd bo ok that wou ld

encompass the large body of methods and data which have s ince been developed.

Since the publication of NBS Handbook No.97, s ignif icant developments related

to radiation protection at electron l inear accelerators have occurred along the

following lines:

(a) Elec tron l inear accelerators for medical and radiographic pu rpose s

operating in the range 440 MeV are now widely accep ted. Th e growing nu m be r

of such machines operating above 10 MeV poses addit ional problems of undesirable

neutron radia t ions and concomitant component act ivat ion.

(b) The re has been a trend toward s tan dardiz ation of radiatio n-pr otec tion

pract ices , and development of nat ional and in ternat ional radia t ion-protec t ion

guidelines for medical accelerators.

(c) The introduction of high-energy, high-power electron machines has

brou ght new typ es of prob lem s and magnified old ones. Th e higher energy has

necessitated provisions for high-energy neutron dosimetry and shielding, muon

dos imetry and shie lding, and t reatm ent of the neu tron skyshine problem . Th e

higher power has aggravated such problems as radioactive air and water and the

possibil i ty of burn-through of shielding by raw electron beams.

(d) Ope rating f lexibil i ty such as mu ltibeam capabili ty has placed new

demands on personnel protect ion sys tems.

(e) Ref in eme nt of measurements of photo nuclea r react ions has made m ore

reliable predictions of neutron production and component activation possible.

These developments include improved consis tency among cross-section measure-

ments with monochromatic photons in the giant-resonance region, as well as new

data on less frequent types of reactions at all energies.

(f) The de velop men t of Monte-Carlo techniq ues to a high degree has made

it possible to undertake otherwise practically intractable calculational problems.

Very useful calculations are now available on electromagnetic cascade develop-

ment , on neutron product ion and t ranspor t , and on muon product ion and

transpor t .

(g) The development of radiation protection practices at other types of

accelerators has also provided a source of inform atio n usefu l at electron acceler-

ators . Co nferen ces on accelerator dosime try and experienc e held in 1965, 1969

and 1971 presented occasions at which world-wide operating experience at

accelerators of all kinds was shared.

(h) Th e growing sensit ivity on the part of the general public to environ-

mental concerns has required a greater degree of attention to radioactive releases.

1


13/342

While these have never been a serious problem at electron accelerators, it still is

desirable to be able to make posit ive s tatements about the amounts produced and

about their disposal.

Since much of this great body of information is scattered widely throughout the

literature, it is the goal of this manual to gather it together in an organized usable

form.

It is s ignif icant that no fatali t ies to p ersonn el have ever resulted f ro m acute

radiation in jury at an electron l inear accelerator . The few serious accidents at

research installat ions that have occurred were by electrocution and ordinary

mechanical in jury. A man ual devoted t o radiological safety is nevertheless usefu l,

because radiation is a 'special ' safety hazard connected with these accelerators and

its management requires more specialized knowledge and instrumentation than do

the programm es of convent ional safe ty .

PURPOSE AND SCOPE OF THE MANUAL

This manual is intended as a guide for the planning and implementation of

radiation p rote ctio n program mes fo r all type s of electron l inear accelerators . I t is

hoped that i t will prove useful to accelerator manufacturers , accelerator users ,

management of insti tutional and industr ial installat ions, and especially to radiation

safety officers and ot her pe rsons responsible for radiation safety. Material is pro-

vided for guidance in the planning and installation stages, as well as for the

implementat ion of radia t ion protect ion for cont inuing operat ions .

Because of their rapidly growing imp ortan ce, the problem s of installation

and radiation safety of standard medical and industrial accelerators are discussed

in separa te section s. Fo r higher-energy research installation s, the basic rad iatio n

protection objectives are the same, but more types of potentially harmful radiation

mu st be considered a nd shielded against. Fo r such facilities, each maj or ty pe of

prob lem is briefly summ arized and references are given to direct the user to mo re

com plete inform at ion in the l i tera ture .

Special discussions are devoted to the radiation protection problems unique

to electron accelerators: thick-target brem sstrahlung, the electromagn etic cascade,

the estimation of secondary-radiation yields from thick targets , and that annoying

opera tional problem , instrum enta l corrections for accelerator duty fac tor . In

addition, an extensive review of neutron production is given which includes new

calculations of ne utro n pro du ctio n in various materials. A recalculation of

activation in a variety of materials has been done for this manual, and specif ic

gamma-ray constants have been recalculated for a number of nuclides to take into

account the contribution of K X-rays. The subjects of air and water activation, as

well as tox ic gas pr od uc tio n in air have bee n specially reviewed. In the se ction on

radiation shielding, published data on bremsstrahlung attenuation have been

2


14/342

reviewed to estimate a consis tent set of at tenuation parameters over a broad range

of pr imary energies . Fur th erm ore, the t reatm ent of mo noch roma t ic ph oto n

reflection of Chilton and Huddleston has been adapted for use with bremsstrahlung

spectra. The discussion of ne utro n shielding uti l izes neu tron tra nsp ort calculations

f rom Oak Ridge which proper ly account for the contr ibut ion of neutron-capture

gamm a rays to the dose equivalent. These data are presented in a for m believed

most convenient for direct use by the radiation protection specialis t .

The present manual does not s tr ive to provide results of great accuracy; this

is very diff icu lt unless all aspec ts of a given situatio n are taken in to ac co un t. Th e

intention is rather to present a balanced treatment of the major kinds of radiation

and provide means to estimate them with s imple algebraic manipulations based on

physically well-grounded interpola tions. Fo r the sake of com pleteness and to

provide addit ional perspective for the user , order-of-magnitude estimates are given

for some radiations of lesser importance.

Betatrons and electron microtrons operating at the same energy produce

essentially the same kind of secondary radiation as electron linacs and the material

given in this manu al is directly ap plicable to them . Ac celera tors which deliver

primary beams of other types of particles , part icularly protons, deuterons or

heavier ions, give r ise to secondary radiation of a somewhat different nature,

owing to the mass and hadronic interactions of the primary particles; the amount

of bremsstrahlung is negligible compared with the intense neutron f luences released

by these particles. The se acc elera tors are no t discussed in this ma nua l.

During the preparation of this manual, an ongoing dialogue was conducted

with accelerator manufacturers and radiation protection specialis ts at several

laboratories (see Ack now ledgem ents) . A num ber of visi ts were ma de to clinics

and research installat ions to gather f irs t-hand impressions of safety practices th at

are actually in use.

The material presented here is of course based on earl ier work by many

persons and organizations. A reasonable attem pt is mad e to acknow ledge, by

citation, the work of individuals where appropriate, but as the f ield of radiation

protection extends over many decades, completeness in this regard is impossible.

Radiation protection manuals which are heavily drawn upon are l is ted in the

General Bibliography (Section 7) . I t is reco mm end ed t hat persons responsible for

radiation protection have a selection of these references available, for addit ional

perspective on the problems and their solutions.

Recommendations for clinical calibrations of beams used in therapy are not

given in this manual, but the reader is referred to reports of international

organizations such as the IAEA and IC RU and othe r authoritat iv e bodies which

deal with this important subject (see Section 7) .

I t should be borne in mind that there may be addit ional regional and local

requirements for radia t ion protec t ion that must be met . Governmen tal author i t ies

and qualif ied experts are best consulted to ensure that each installat ion is operated

in compliance with all legal requirements .

3


15/342

TABLE I . FREQUENTLY USED SYMBOLS AND UNITS

Na me Sy mbo l

Uni ts

Na me Sy mbo l

SI Special Conve rsion facto rs

Abso rbed do se

D

gray (Gy)

rad (rad) 1 rad = 10 mG y = 10 mJ kg "

1

Abso rbed do se ra te

D

G y s"

1

rad s "

1

1 rad- s"

1=

1 0 mG y s "

1

Ex po sure

X

co ulo mb per k i lo g ra m (C k g '

1

)

ro ntg en (R)

1 R = 2 5 8 /^C k g"

1

Exposure rate

X

C ' k g - ' - s "

1

R s '

1

1 R s"

1

= 258 fiCk g"

1

s

_1

Dose equivalent H

(d imens io ns o f J

-

k g"

1

)

rem

Dose equivalen t rate H

-

re m s"

1

Activ i ty

A

becquere l (Bq) cur ie (Ci ) 1 Ci = 3 7 G B q= 3 .7 Xl O ^ s"

1

Quality factor

Q

-

-

Electro n k inet i c energ y

E

MeV

-

1 MeV= 1 .6 0 2 X 1 0 "

13

J

Incident or initia l

kinetic energy

E

0

MeV

Pho to n energ y

k

MeV

Useful conversions

1 Bq = 1 radioactive dis integr ation per seco nd = 1 s"

1

= 2 7 .0 2 7 pCi

1 G y = 1 J kg "'= 1 0 0 ra d

1 eV = 1 .6 0 2 X 1 0 ~'

19

J , a pprox.

1 MeV = 1 .602 X 10"

13

J= 1.602 X 10"

13

kg G y = 1 .6 0 2 X 1 0 "

8

g - ra d= 1 .6 0 2 X 1 0 "

6

erg

1 W =

1

J - s " ' = 1 V A

Abso rbed do se co rrespo nding to a n ex po sure X o f 1 C k g"

1

: to air: D = 33. 7 Gy

t o t i ss u e : D = 3 6 . 4 G y ( C o - 6 0 )


16/342

TERMINOLOGY AND UNITS

Where possible, the terminology and units correspond to those defined in

ICRU Re por t 19 (see Bibliography, Section 7) . Tab le I gives freq ue ntly used

symbols and units . (See Ap pen dix A fo r addit ion al useful physical and num erical

constants .)

Note

The qu est ion o f an Si-cohere nt unit with a special name for dose equivalent H is under-

going review. The s ievert (Sv) , whic h is the absorbed d ose D ( in G y) mu lt ip l ied b y

dimensionless modifying factors ( in part icular the qual i ty factor Q) has been proposed

to the C onfer enc e Ge'n&ale des Poids et M esures (CGPM) by the Internat ional

C ommis s ion on R ad ia t ion U n i t s an d Meas u remen ts ( I C R U ) an d th e I n tern at ion a l C ommis -

s ion on R adiological Pro tect ion (ICRP ). The s ievert wo uld s tand in the same relat ionship

to the gray as the rem do es to the rad. S ince a f inal resolut ion o f th is matter has not bee n

made at the t ime of publicat ion, values of dose equivalent H are g iven in rem in th is manual .

In all other instances radiation quantities are given in

both

the S l-coh eren t units and

the exis t ing special units . Also no te that no special S i-cohe rent unit has been propo sed to

the CGPM for exposure X; the S i-derived unit C

kg"

1

is used fo r expo sure.

ACKNOWLEDGEMENTS

The author gratefully acknowledges the kind hospitali ty and support of the

International Atomic Energy Agency and the Stanford Linear Accelerator Center

in the preparation of this manuscript , and particularly thanks F.N. Flakus and

R.C. McCall for their personal help and enco urage men t.

The au thorisdeeply i nd eb ted to F.H . A ttix , G.R. Higson, M. Lad u, T.G. M artin III,

R.C. McCall, T. Nakamura, C.S. Nunan, J. Rassow and K. Tesch for valuable

comments on a preliminary draft , and to my colleagues D.D. Busick, T.M. Jenkins,

K.R. Kase, W.R. Nelson and G.J . Warren of the Stanford Linear Accelerator

Cen ter , and R.H. Th om as of the Law rence Berkeley Labo rator y, for generously

sharing their knowledge and experience.

Many oth er individuals, representing a large nu mb er of organizations, were

extrem ely coope rative and helpf ul in supplying usefu l info rm atio n. These include :

R. Alvarez, L. Arm stron g, A. Asam i, M.L. Berger, B. Berm an, J. Bly, J. Bro berg,

A. Burrill, R. Byers, A.B. Ch ilton, T .R . Ch ippe nda le, J.B. Czirr, J. Fen ger,

H. Fu ji ta, E.G. Fuller , G. Gilbert , T.F . Godlove, T.W. Gru new alt , D. Hankins,

P. Harda ker, T.G. Hob bs, J . Jasberg, R. Jean , R. Joh nso n, J . Kaehler ,

M.J. Ka raffa, C.J . Karzm ark, N.N. Kaushal, N.L. Kay, J .G. Kelliher, E,A. Knap p,

J.D. Koen ig, S. Ku rihara , M. Lara, J. Leb acqz , J.E . Leiss, G . Loe w, P. Ma schka,

5


17/342

T.P. M cR eyn olds, B. M ecklenb urg, B. Me yer, V. Mo re, R.B. Neal, P. Ogren,

S. Pen ner, F. Peregoy , E. Petersilka, V. Price, D. Reid, J.C. R itte r, R. Ro rd en ,

R. Ry an, A. Sm ith, W. Sm ith, V. Stieber, I .A. Ta ub, G. Toch ilin, G. Trim ble,

W. Tu rchin etz, Yu.P. Vak hrushin, R. Van de Vyver, N. Van Hoo yd on k,

D. Walz, K. W hitham , D. Willis, U. Yelin, and man y other s wh o provided

information about specif ic accelerator installat ions or discussed certain portions

of the material.

The author acknowledges with deep appreciation the considerable help in

the preparation of this manuscript by V. Smoyers and personnel of the SLAC

Dra fting De part me nt unde r the leadership of T. Hu nter . D. Dup en, W. Field

and A. Schwa rtz provided very helpful advice at cr i tical mo me nts .

6


18/342

1. USES AN D CHARACTERISTICS OF


1.1. Fields of app licatio n

Several decades of technological development have culminated in the modern

microwave electron l inear accelerator , or electron l inac, an instrument useful in

medicine, industry and science [1,2, 3] . The technologies combined in this

simple and powerful tool are high-power pulsed microwave generation, high-

vacuum tec hno logy , electronics , and metal forming and assembly. Originally

developed as a research instrument to s tudy the basic s tructure of matter , i t has

become useful in several other important ways.

(a) Medical applications

In radiation therapy, second- and third-generation electron l inacs are widely

em ploye d in the treatm en t of cancer. They o ffe r the advantages of s implicity

and reliabil i ty, higher output, larger treatment f ields, and the choice of both

electron and p ho to n irradiations. Th e higher energies are usefu l because of the

greater penetration of the radiation to treat deep-lying tumours and afford a

greater degree of pr ot ec tio n to the skin. A small foca l spot allows precise beam

defin it ion. Space requ irem ents for the accelerators are mo dest and they are readily

ada ptab le to rota tion al ther apy . Both because of i ts societal imp ortan ce and in

terms of numbers of accelerators in operation (over 800), cancer therapy is the

leading application of the electron l inear accelerator [4, 5,6] .

(b) Industrial applications

High-intensity radiography is now an accepted, s tandard application of the

electron linac, such as in the X-ray inspection of large welds, castings, complex

assemblies and solid pro pe llan ts [7], Ra diat ion processing app lication s [8] includ e

curing of pain t and adhesives, poly me rization of plastics , foo d preservation [9]

and steri l ization of heat-sensit ive medical products [10].

(c) Research applications

A third m ajo r cate gory of uses is in scien tific research . Resea rch in nuclea r

physics employs linacs operating in the range 25500 MeV, generally using the

copiously produ ced ph ot on s to s tudy nuclear s tructures. Facil i ties for studies

using neutro n t ime-of- fl ight and m onoenerget ic pho ton s have perm it ted mu ch

greater detail in the experimental results than previously possible [11, 12].

7


19/342

Laboratories doing research in elementary particle physics use l inacs producing

electron beam s with energies as high as 22 G eV and pos itron beam s up to

15 GeV [3] (1 GeV-1000 MeV). The extremely shor t wavelength corresponding

to the electron or positron momentum (1CT

1S

cm at 20 GeV) permits the sub-

struc ture of the mu ch larger pr oto n and ne utr on (radius 1.2X10"

13

cm) to be

explored.

Linacs are used as injectors for electron synchrotrons and electron/positron

storage rings fo r ele me nta ry partic le research . Th e discovery in 197475 of

massive (compared with the nucleon) elementary particles at the e

+

-e"storage

rings is considered on e of the m ost imp orta nt scientif ic results of recent t imes

because i t reveals the existence of a previously unknown property of matter , with

implications concerning nuclear substructure [13].

Pulse radiolysis is a field of chemistry which uses to advantage the short

radiation pulses available from electron l inacs to s tudy the dynamics of chemical

reactions, particularly of free radicals.

A list of experimental uses under study might include such diverse subjects

as: th e use of inten se beam s of negative pi me sons (7r~) fo r cancer th era py , pro -

duction of short- l ived isotopes for prompt use in nuclear medicine, earth tunnell ing

and free-electron lasing.

1.2. Ty pes of electron linear accelerator installations

The electron l inear accelerator i tself is fundamentally a conducting tube,

usually of copper, accurately shaped to contain an electromagnetic wave of the

pro pe r cha racteristic s - a kin d of waveguide [14, 15, 16]. Th e beam energy is

proportional to the length and to the electr ic f ield s trength within the cavity or ,

equivalently, to the square roo t of the microwave pow er inserted. Typical

gradients achieved l ie in the range 2 - 4 M eV /ft . Because the electrons achieve

relativistic velocities quickly, the spacing of cavities within the tube is uniform

almost thro ug ho ut i ts length. A high-energy accelerator differs fro m a low-energy

machine mainly in i ts total length.

Tw o differe nt config uration s are in mo dern use. In the travelling wave

accelerator (Figs 1, 2), microwave power is supplied to the input of the accelerator

section and travels to the other end, remaining at all times in phase with the

moving electron b unche s. The accelerator interior is part i t io ned into accelerating

cavities dimensioned in such a way that the phase velocity of the microwave field

equals the electron velocity.

Ano ther conf igurat ion is the

standing-wave accelerator

[17, 18] in which

additional side cavities provide a 180 phase shift between accelerating cavities

(Fig.3) . This type has the advantage of being less sensit ive to tem per atu re or

dimensional v ariations and achieves the same beam energy in a shorter len gth.

8


20/342

FIG.l. A ten-foot (^3.0 m) travelling-wave accelerator section for SLAC . With a 16-MW

klystron (peak RFpower), the energy added by such a section is 40 MeV . The uniform

partitioning into RF cavities by annular disks is easily seen.

(Reproduced with kind permission of the Stanford Linear Accelerator Center and the Energy

Research and Development Administration.)

9


21/342

FIG.2. Accelerator disks and cylinders. These compon ents are assembled to form the 10-ft

(=3.0 m) sections show n in Fig.l.


Research and Developm ent Adm inistration.)

B E A M

C H A N N E L

A C C E L E R A T I N G

C A V I T Y

C O U P L I N G

C A V I T Y

FIG.3. Structure of a standing-wa ve accelerator. The coupling cavities provide a phase

change such that the accelerating cavities ma intain a 180 pha se shift with respect to each other.

(Reprodu ced with kind permission of E.A. Knapp , th e Los Alam os Scientific Labora tory and

Review of Scientific Instruments.)

1 0


22/342

Microwave power f or low energies is generally develope d by ma gnetro ns, bu t

all higher-energy accelerators use klystron s. The nom inal frequ enc y of 300 0 Hz

(wavelength 10 cm in free space at 299 8 MHz) is usually used. Peak R F pow ers

generated per uni t are 2 - 5 MW (magnetrons) and 2 0 - 4 0 MW (klys t rons) .

The following components are common to all types of installat ions:

(a) Th e injec tor , containing the gun or electron 'so urc e' ;

(b) The accelerator i tself, com posed of one or mo re sections, fed by

separate microwave generators;

(c) Th e microwave generato rs: one or mo re ma gnetro ns or klystro ns,

driven in phase;

(d) A m od ula tor to energize each microwave genera tor;

(e) A target an d/o r beam dum p to provide usefu l seconda ry radiation s

and stop the electrons.

In add it ion, most installat ions have at least one beam -transp ort m agn et. Most

medical accelerators operating above 6 MeV are equipped with a magnet which is

an integral part of th e apparatu s which deflec ts the beam by 90 or 27 0. Research

installat ions may also have secondary beam lines, transporting a variety of particle

types pho tons , e lect rons , pos i t rons and mesons .

Three categories of installat ions with s imilar radiation protection problems

are easily ide ntifia ble : (a) med ical, (b) indu strial, and (c) resea rch. Th ese

categories may differ somewhat in the types of radiations to be protected against ,

but more so in the physical layout and movements of personnel and members of

th e general pub lic arou nd th em . Special needs of these type s of installat ions are

discussed where appropriate, and descriptions of typical installat ions are given.

I t is hoped that useful information for meeting the requirements of novel or

unique installat ions will be found in this manual, al though every case cannot be

foreseen.

1.3. Parameters of electro n linear accelerators

A lis t of physical parameters of the two-mile Stanford Linear Accelerator

(Fig.4) is given in Tab le II. A ltho ug h the exa mp le chosen is at present th e highest-

energy l inac, most of i ts parameters are quite representative of many other

travelling-wave a ccelerators if the differe nce s related to i ts great length (mu ltiplici ty

of sections and there fore of beam energy and pow er) are tak en into acco un t. The

particularly unique features of the SLAC facil i ty are the interlaced-multiple-beam

capabili ty, the abil i ty to accelerate also positrons and polarized electrons to high

energies, and a special facility for extremely short (10 ps) beam pulses.

Tables III, IV and V provide an overview of three classes of linear accelerator

installat ions. I t is seen tha t the developm ent in medical accelerators within the

past decade (Table III) has been towa rd a capabil i ty for isocentr ic the rap y using

11


23/342

FIG.4. Aerial view of the Stanford Two-M ile Accelerator (SLAC ), a modern high-energy

facility for elementary-particle research. The Research Area with multiple-beam capability

is in the foreground. The electron-positron storage ring SPEA R is to the lower right. The

360 beam pu lses accelerated per second are shared by as many a s six different beam paths,

each with separately adjustable energy, current and pulse length.


Research and Developm ent Adm inistration.)

bo th electrons and pho ton s [4] , The maxim um usefu l energy appears to be

approximately 40 MeV. The radiation characteris t ics at each energy are surpris ingly

similar amo ng these m ode rn facil it ies , reflecting a general consensus am ong

manufacturers and users .

Ac celera tors for indus trial radio grap hy are surveyed in Tab le IV. The very

high ou tp ut s of these machines may pose a great poten tial hazard to o perating

personnel in industrial settings.

Table V contains an abbreviated l is t of physical parameters of representative

ope ratin g research and special-purpose installa tions. Th ere is great variety in the

capabili t ies of these installat ions, reflecting the purposes to which they are applied.

Figure 5 illustrates the general rise in beam power with accelerator energy.

Text continued on p.24

1 2


24/342

TABLE I I . PHYSICAL PARAM ETERS OF THE STAN FORD TWO-MILE

ACCELERATOR (SLAC)

Accelerator length

1 0 0 0 0 f t ( 3 0 4 8 m )

Length between feeds

1 0

ft

( 3 . 0 4 m )

Number of acc e lera tor sect io ns

960

Number of klystrons

245

Peak power per klys tro n 20 - 40 MW

Beam pulse repet i t ion rate 1 - 360 p u ls e s / s

RF pu lse length 2 .5 ixs

Fi l l ing t ime

0 .83 us

Electro n en erg y, unloaded

22. 8 GeV (m ax )

Electr on en erg y, loaded 21 .5 GeV

Electron peak beam current

70 mA (max)

Electron average beam current

40

fj,A

(max)

Electron average beam power 800 kW (max)

Electron beam pulse length

10 ps - 1. 6 jxs

Electron beam energy spread (max)

0.5%

Posi tron energy

15 GeV (max)

cl

Pos i tron average beam current

0.5 fxA

Multiple beam capability

6 interlaced beams

with independently ad-

justable pulse length,

en er gy , and cur ren t

Operating frequency

2856 MHz

For 140 kW of incident elec tr on beam power at po sitron so ur ce

located at one-third point a long accelerator length.

13


25/342

TABLE II I . RADIATION PARAMETERS OF MEDICAL ELECTRON LINEAR ACCELER ATORS INTRO DUCED SINCE 1965

A p p r o x .

da t e o f

i n t r o d u c t i o n

M a n u f a c t u r e r

Beam ener g i es

i n m oda l i t y

P h o t o n s E l e c t r o n s

( M V) ( M eV)

T y p e o f

m o u n t o r

m o t i o n

T o t a l

s t r u c t u r e P o w e r

l e n g t h s o u r c e

and t ype

T r a n s p o r t

m a g n e t ( s )

M a x i m u m p h o t o n

M a x i m u m

_ , field size

O O ' G y . m ' . m l n - ' )

( p h o t o n s )

( r a d - m - m m )

m

' a t 1 m )

( n a t t e n e d )

N o m i n a l

l e a k a g e

r ad i a t i on**

( p h o t o n s )

(%)

1 9 6 5

1 9 6 5

1 9 6 7

1 9 6 7

1 9 6 8

1 9 6 9

1 9 6 9

1 9 7 0

1 9 7 0

S L 75 / 10 P h i l i p s

M E L

L UE 5

L UE 25

M e v a t r o n

V I

M e v a t r o n

XII

E f r e m o v

E f r e m o v

A p p l i e d

R a d i a t i o n

A p p l i e d

R a d i a t i o n

M L - 1 5 M I I B M i t s u b i s h i

T her a p i 4 S HM

N u c l e a r

7 - 1 0 4 - 1 0

5

1 0 , 1 5 1 0 - 2 5

T h e r a c 4 0 C G R - M e V 1 0 , 2 5 7 - 3 2

S agg i t a i r e AE CL ( 40 )

L M R 13 T osh i b a

Cl i nac 4 Var i an

8 , 1 0 5 -

1 2 8 -

I s o c e n t r i c

1 0 0 c m S A D

I s o c e n t r i c

1 0 0 c m S A D

S t a t i o n a r y

0

-30

+ 4 5

I soce n t r i c 105

1 0 5 c m S A D ( 3 7 0

wi t h p i t )

I s o c e n t r i c

1 0 0 c m S A D

I s o c e n t r i c

80 cm S AD

I s o c e n t r i c

1 0 0 c m S A D

I s o c e n t r i c

1 0 0 c m S A D

I s o c e n t r i c

1 0 0 c m S A D

2 1 0

3 6 0

3 7 0

3 7 0

3 9 0

3 6 5

2 . 25 m , T W 2 M W

M a g n e t r o n

T W 1 . 8 M W

M a g n e t r o n

6 . 5 m , T W 20 M W

( t w o K l y s t r o n

s e c t i o n s )

6 . 0 m , T W 9 M W

( t w o K l y s t r o n

s e c t i o n s )

1.6 m, TW

0. 3 m , S W

9 5 6 0 0 ( 3 0 0 W e l e c t r o n s 3 0 X 3 0

( a p p r o x . ) a t 8 M e V )

c

18 X 18

(2 0 X 2 0 )

d

4 . 8 M W

M a g n e t r o n

2 MW

M a g n e t r o n

1.0 m, SW 2 MW

M a g n e t r o n

1 . 3 m , S W 2 M W

M a g n e t r o n

1 . 7 m , T W 5 M W

K l y s t r o n

0 . 35 m , S W 2 M W

M a g n e t r o n

+ 37

- 3 7

+ 37

- 127

105

( a p p r o x . )

N o n e :

s t r a i gh t

a h e a d b e a m

2 6 1

a c h r o m a t i c

2 6 1

a c h r o m a t i c

N o n e :

s t r a i g h t

a h e a d b e a m

4 0 0 ( 1 0 0 0 )

( 2 k W e l e c t r o n s )

0

3 8 X 38

3 0 X 3 0

4 0 X 4 0

4 0 X 4 0

4 0 X 4 0

3 0 X 30

4 0 X 4 0

0.1

0.1

0.1

0 . 0 3

b

0 . 0 2

0.1

G i n a c 3 5 V a r i a n

8 , 2 5 7 - 2 8

I s o c e n t r i c 3 6 0

1 0 0 c m S A D

2. 25 m , T W 20 M W

K l y s t r o n

+ 57

- 9 0

1000 35 X 35

( 5 k W e l e c t r o n s )

8


26/342

Approx.

date o f

int roduct ion

Manufacturer

Beam energies

in m oda l i t y

3

Photons Electrons

( M V) ( M eV)

Type of

m ount or

motion

Total

s t ructure

length

an d type

Power

Transport

source

magnet(s)

2 MW 266

Magnetron

achromatic

2 MW 262

Magnetron

achromatic

2 MW

266

Magnetron

achromatic

2 MW

None:

Magnetron

straight

ahead beam

4 . 8 M W 105

Magnetron (approx.)

5 MW 270

Klystron

achromatic

5 M W

95

Magnetron (approx.)

2 MW

None:

Magnetron straight

ahead beam

2 MW

None:

Magnetron

straight

ahead beam

5 MW 270

Klystron achromatic

S MW

266

Klystron achromatic

2 MW 270

Magnetron

achromatic

2 M W

None:

Magnetron straight

ahead beam

Maximum photon

output

( 1 0 "' G y m ' min" ' )

( r a d - m

2

*m i n

- 1

)

( f lat tened)

Maximum

field size

(photons)

(c m

3

at 1 m)

Nominal

leakage

radiation*

5

(photons)

(%)

1 9 7 0

1971

1 9 7 2

1 9 7 2

1 9 7 2

1 9 7 3

1 9 7 3

1 9 7 3

1 9 7 4

1 9 7 4

1 9 7 4

1 9 7 5

Dynaray 4

Therac 6

Neptune

Radiation

Dynamics

CGR-MeV

AECL

Dynaray 10 Radiation

Dynamics

L M R 1 5

Toshiba

Therac 2 0 CGR-MeV

Saturne AECL

S L 75/ 20 Philips

M E L

Clinac 1 8 Varian

Dynaray 1 8 Radiation

Dynamics

Clinac

12

Varian

Clinac 6X Varian

4

6

8 3 - 1 0

4 -

1 0 1 0 - 1 6

1 0 , 1 8 6 - 2 0

8 , 1 6 5 - 2 0

6-12 5^18

8

( 6 )

6 - 1 2

( 4 - 9 )

Isocentric

1 0 0 c m S A D

Isocentric

1 0 0 c m S A D

Isocentric

1 0 0 c m S A D

Isocentric

80 / 100

c m

S A D

Isocentric

1 0 0 c m S A D

Isocentric

1 0 0 c m S A D

Isocentric

1 0 0 c m S A D

Isocentric

8 0 c m S A D

Isocentric

8 0 c m S A D

Isocentric

1 0 0 c m S A D

Isocentric

1 0 0 c m S A D

Isocentric

1 0 0 c m S A D

Isocentric

8 0 c m S A D

3 7 0

370

370

420

420

370

360

380

3 6 0

370

360

360

0 . 7 5 m , T W

1. 1 m , T W

2. 3 m , T W

0. 3 m , S W

1. 7 m , T W

2. 3 m , T W

2. 5 m , T W

0. 3 m , S W

0 . 2 5 m , S W

1. 4 m , S W

2. 3 m , T W

1. 2 m , S W

0. 3 m , S W

3 0 0

2 5 0

3 0 0

2 2 5

4 0 0 ( 9 0 0 W

electrons a t

1 0 - 1 5 MeV)

c

2 2 4

5 0 0

3 5 0

3 5 0

192

3 0 X 3 0

4 0 X 4 0

3 5 X 35

4 0 X 4 0

3 0

X

30

4 0

X

4 0

3 0

X

3 0

3 0 X 3 0

35 X 35

3 5 X 35

3 5 X 3 5

4 0 X 4 0

0.1

0.1

0.1

0 . 0 5

0.1

0.1

0.1

Se efootnotes a t end of table.


27/342

TABL E III. (con t.)

A p p r o x .

da t e o f

i n t r o d u c t i o n

M ode l

Beam ener g i es

i n m o d a l i t y

3

M a n u f a c t u r e r

P h o t o n s

( M V)

T ype o f

1

m o u n t o r

E l e c t r o n s m o t i o n

( M eV)

T o t a l

s t r u c t u r e P o w e r

l e n g t h s o u r c e

and t ype

M a x i m u m p h o t o n

_ o u t p u t

T r an s po r t ( 1 0 " G y m ' - m i n " )

m a g n e t ( s ) (

r a d

.

m

2

( f l a t t e n e d )

M a x i m u m

Held size

( p h o t o n s )

( c m

2

at 1 m )

N o m i n a l

l eakage

r ad i a t i on**

( p h o t o n s )

(%)

1 9 7 5

S L 7 5 / 5

Phil ips

M E L

4 - 6

-

I s o c e n t r i c

1 0 0 c m S A D

4 2 0

1 . 2 5 m , T W

2 M W

M a g n e t r o n

9 5 3 5 0 4 0 X 40 0 . 1

1976 T her a c 10

N e p t u n e

C G R - M e V

A E C L

9

6 - 1 0

I s o c e n t r i c

1 0 0 c m S A D

370 1 . 2 m , S W 2 M W

M a g n e t r o n

2 6 2

a c h r o m a t i c

300 40 X 10 0 . 1

1 9 7 6

D y n a r a y 6 R a d i a t i o n

D y n a m i c s

6

-

I s o c e n t r i c

1 0 0 c m S A D

370 1 . 0 m , T W

2 M W

M a g n e t r o n

2 6 6

a c h r o m a t i c

3 0 0

35 X 35

0 . 1

1 9 7 6

L UE 15M

E f r e m o v

15

1 0 - 2 0

I s o c e n t r i c

1 0 0 c m S A D

120 2 . 6 m , T W

9 MW

M a g n e t r o n

2 7 0

a c h r o m a t i c

3 0 0

( 1 . 5 k W e l e c t r o n s )

0

3 0 X 3 0

2 0 X 2 0

d

0 . 1

0 . 2

b

1 9 7 7

M e v a t r o n

X X

S i e m e n s

10, 15

3 - 1 8

I s o c e n t r i c

100 cm S AD

370 1 . 3 m , S W

7 M W

K l y s t r o n

2 7 0

a c h r o m a t i c

300 40 X 40

0 . 1

1 9 7 7

Cl i nac

6 / 1 0 0

Var i an

6

I s o c e n t r i c

1 0 0 c m S A D

360 0 . 3 m , S W

2 MW

M a g n e t r o n

N o n e :

s t r a i gh t

a h e a d b e a m

2 0 0 4 0

X

4 0

0.1

1 9 7 7

C l i n a c 2 0 V a r i a n 1 5 6 - 2 0

I s o c e n t r i c

1 0 0 c m S A D

3 6 0 1 . 6 m , S W

5 MW

K l y s t r o n

2 7 0

a c h r o m a t i c

500

35 X 35

0 . 1

1 9 7 7

E M I F O U R

EMI

T h e r a p y

4

I s o c e n t r i c

1 0 0 c m S A D

360 0 . 3 m , S W

2 MW

M a g n e t r o n

N o n e :

s t r a i g h t

a h e a d b e a m

2 2 0 4 0 X 4 0

0 . 1

1 9 7 7

E M I S I X

E M I

T h e r a p y

6

I s o c e n t r i c

1 0 0 c m S A D

360 0 . 3 m , S W

2 MW

M a g n e t r o n

N o n e :

s t r a i gh t

a h e a d b e a m

2 2 0

4 0 X 40 0 . 1

1 9 7 8

L UE S M

E f r e m o v

4 - 5

4 - 5

I s o c e n t r i c

1 0 0 c m S A D

120

0 . 6 m , T W

3 M W

M a g n e t r o n

N o n e :

s t r a i gh t

a h e a d b e a m

2 0 0 3 0 X 3 0

2 0 X 2 0

d

S L 7 5 / 1 4 P h i l ip s 8 , 1 0 4 - 1 4

M E L

I s o c e n t r i c 3 6 0

1 0 0 c m S A D

2. 25 m , T W 2 MW

M a g n e t r o n

D a t a i n p a r e n t h e s e s a r e n o n - s t a n d a r d o p t i o n s o f f e r e d b y m a n u f a c t u r e r .

A v e r a g e d o v e r 1 0 0 c m

3

a t 1 m . W her e t wo va l ues a r e g i ven , t he f i r s t r e f e r s t o pa t i en t p l an e , t he seco nd app l i e s t o r oom sh i e l d i ng .

V e r t i c a l , r o t a t i o n a l a d j u s t m e n t .

W h e r e t w o f i e l d s i z e s a r e g i v en , t h e f i r s t r e f e r s t o p h o t o n b e a m t h e r a p y , t h e s e c o n d t o e l e c t r o n t h e r a p y .

P r i m a r y e l e c t r o n b e a m e x t r a c t e d i n r e s e a r c h m o d e .


28/342

TABLE IV. RADIATION CHARAC TERISTICS OF ELECTRON LINEAR ACCELE RATOR S FOR INDU STRIAL

R A D IO G R A P H Y

Ma nufa cturer Mo del

No mina l bea m

energy

( M e V )

RF po wer so urce

(ma g netro n

o r k ly s tro n)

Ma x imum X-ra y o utput

( u n f l a t t e n e d )

( G y m

2

- s"

1

) ( r a d - m

2

- m i n ' )

M a x i m u m

field s ize

(at 1 m)

( c m )

N o m i n a l p h o t o n

leakage radiation

(per cent o f usefu l

bea m a t 1 m)

CG R MeV Nep tune 6 6

M

0 .1 3

7 5 0 5 0 (d ia . )

0 .1

C G R M e V N e p t u n e 1 0

10

M

0 .3 3

2 00 0 50 (dia .) 0 .1

E f r e m o v LUE-15-1.5 15 M 1.7 10 000 3 0 (dia.) 1.0

Efremo v

L U E - 1 0 - 1 D

10

M

0 .3 0

1 8 0 0

2 2 (d ia . )

1 .0

E f r e m o v

L U E - 1 0 - 2 D

10

M

0 .8 3

5 0 0 0 2 5 (d ia . )

1 .0

E f r e m o v L U E - 1 5 - 1 5 0 0 0 D 1 5

M

2.5

1 5 0 0 0

4 0 (d ia . )

1 .0

Efremo v

L U E - 5 - 5 0 0 D

5

M

0 .0 8

5 0 0

3 5 (d ia . )

0 .2

EMI Thera py

Radiograf 4

4

M

0 .0 8

5 0 0

26 X 35

0.5

Mitsubishi

ML-1 Rl l

0 .9 5

M

0 . 0 0 3

2 0 3 0 (d ia . )

0 .1

Mitsubishi

ML-1 RIII

0 .4 5

M

0 .0 0 0 2 5 1 .5 3 0 (d ia . ) 0 .1

0 . 9 5 0 . 0 0 2 5

15

0.1

Mitsubishi

ML-3 R

1.5

M

0 .0 1

5 0 3 0 (d ia . )

0 .3

Mitsubish i ML-5 R 3

M

0 .0 5

3 0 0 3 0 (d ia . )

0 .3

Mitsubish i ML-5 RII

4

M

0 . 0 6

3 5 0 3 0 (d ia . ) 0 .3

Mitsubish i ML-1 OR 8 M 0 .3 3 2 0 0 0 30 (dia .) 0 .2

Mitsubishi

ML-1 5 RII

12

K

1.2

7 0 0 0

30 (dia .) 0 .1


29/342

TABLE IV (cont . )

. , , Ma x imu m X-ra y o utpu t Ma x imum No mina l pho to n

Nom inal beam RF pow er source , . . . , . . , .

, , , (un flat ten ed) field s ize leakage radiation

Manu facturer Mode l energy (ma gnet ron , ^ , . . ^ ,

. . . . | , \ (at 1 m) (per cen t of usef ul

( M e V ) o r k l y s t ro n ) 2 - 1 , , j 2 -k / . ,

( G y m s ) ( r a d - m m i n ) ( c m ) b e a m a t 1 m )

Ra dia t io n Super X 6 0 0 4 M

D y n a m i c s

Ra dia t io n Super X 2 0 0 0 8 M

D y n a m i c s

Ra dia t io n Super XX 1 2 K

D y n a m i c s

Varian Linatron 20 0 2 M

Va ria n L ina tro n 4 0 0 4 M

Va ria n L ina tro n 2 0 0 0 8 M

Varian Linatron 60 00 15 K

0 .1 6 0 0 3 0 (d ia . ) 0 .1

0 .3 3 2 0 0 0 3 0 (d ia . ) 0 .1

1.0 6 00 0 30 (dia .) 0 .1

0 .0 3 1 7 5 7 7 X 7 7 0 .0 2

0 . 0 7 4 0 0 3 9 X 3 9 0 . 1

0.33 2 00 0 55 (dia .) 0 .1

1.0 6 00 0 27 (dia .) 0 .1


30/342

TABLE V. RADIAT ION PARAMETERS OF RESEARCH AND SPECIAL-PURPOSE ELECTRO N LINEAR ACCELER ATORS

T y p i c a l h i g h - p o w e r o p e r a t i o n ( a p p r o x . )

I n s t a l l a t i o n

l o c a t i o n

N o m i n a l

p e a k

e n e r g y

( M e V )

M a c h i n e u s e

S p e c i a l c a p a b i l i t i e s

N u m b e r a n d

t ype o f

s e c t i o n s '

3

R F

s o u r c e

c

P e a k

c u r r e n t

( m A )

E n e r g y

( M e V )

T

P

C

MS)

P u l se

r a t e

( H z )

D u t y

f a c t o r

(%)

E l e c t r o n

p o w e r

( k W )

1 A m s t e r d a m I K O 5 0 0

N u c l e a r p h y s i c s

N u c l e a r c h e m i s t r y

n ( 0 - S 0 0 M e V )

L a r g e d u t y f a c t o r

25 T W ( S ) 12 K ( 14) 10 25 0 50 25 00

1 0 . 2 0 0

1

2 A r g o n n e 2 2 N u c l e a r p h y s i c s

N u c l e a r c h e m i s t r y

n ( 2 2 0 M e V )

35- ps pu l ses

2 T W ( L )

2 K ( 20 )

2 5 0 0 1 4 1 0

1 2 0 0 . 1 2

4 5

2

3 B a r i l o c h e 3 0 N u c l e a r p h y s i c s

1 0 1 0 0 n s p u l s e s

1 T W ( S ) 1 K 30 0 25 1 . 2

2 0 0

0 . 0 2 4

1 . 8

3

4 B e d f o r d R A D C 1 2 R a d i a t i o n r e s e a r c h

1 T W ( L ) 1 K ( 10 ) 550 10 4 . 3 180

0 . 08 S . O

4

5 Ber l i n BAM 35

A c t i v a t i o n a n a l y s i s

N e u t r o n r a d i o g r a p h y

R a d i a t i o n p r o t e c t i o n

2 T W ( S ) 1 K 180 30

4 300

0 . 1 2 6 . 5 5

6 Ber l i n HM I 18

P u l s e r a d i o l y s i s N a n o s e c o n d p u l s e s

1 T W ( L ) 1 K ( 10 )

BOO

12

5

50

0 . 0 2 5 2 . 5 6

7 B e t h e s d a A F F R I

5 5

R a d i a t i o n r e s e a r c h H i g h c u r r e n t

6 T W ( S ) 4 K 100 0

3 0

1.0

1 0 0 0

0

.1 3 0

7

8 B o e i n g ( S e a t t l e ) 3 0

R a d i a t i o n r e s e a r c h

3 T W ( S ) 1 K 110 0 11 . 5

5

3 0

0 . 0 1 5 1 . 9

8

9 B o l o g n a 1 2 R a d i a t i o n c h e m i s t r y

R a d i a t i o n b i o l o g y

R a d i a t i o n p h y s i c s

S e l e c t a b l e p u l s e w i d t h

H i g h c u r r e n t

11 A i n 10 - ns pu l se

T W ( L )

1 K ( 1 0 )

1 4 0 0

6

5

3 0 0 0 . 1 5 1 2

9

1 0 B o n n 3 5

S y n c h r o t r o n i n j e c t o r

1 T W 1 K ( 25 )

8 0 0

2 0

1

50 o.oos

0 . 8

10

11 Cor ne l l

2 4 6


6 T W 3 K 100

150 2 . 5 60

0 . 0 I S 2 . 3

11

1 2 D a r e s b u r y

4 3


4 T W

2 K ( 3 0 ) 5 0 0

4 3

0 . 7 3 5 3

0 . 0 0 4 0 . 8

12

1 3 D a r m s t a d t 7 0


( e e ' ) r e s o l u t i o n 3 0 k e V 2 T W ( S )

1 K 60

7 0

5 . 5

I S O

0 . 0 8 4 . 0 13

14 DE S Y I

15 DE S Y I I

4 0 0

5 0


S e c o n d i n j e c t o r

e

+

( 2 5 0 3 8 0 M e V )

D O R I S s t o r a g e r i n g s

P E T R A s t o r a g e r i n g s

14 T W

5 T W

1 4 K ( 2 5 )

5 K ( 6 )

2 0 0

7 0

5 0 0

4 0

2

1

5 0

50

0 . 0 1

O.OOS

10

0 . 2

14

15

16 F r asca t i

4 5 0 S t o r a g e r i n g i n j e c t o r

e

+

( 6 0 3 2 0 M e V )

A D O N E s t o r a g e r i n g s

12 T W ( S )

6 K ( 20 )

100

4 0 0 3 . 2 2 5 0

0 . 0 8

4 0

16

1 7 G e e l B C M N I S O N u c l e a r p h y s i c s 10 A i n 3 - ns pu l se 1 S W ( S )

2 T W ( S )

3 K 1 5 0 0 9 0

0

.1

9 0 0 0 . 0 0 9 1 2 17

1 8 G h e n t 9 0 N u c l e a r p h y s i c s

e * ( 1 0 - 4 0 M e V ) 2 T W ( S )

2 K ( 20 ) 25 0

7 0

2 . 5

3 0 0 0 . 0 7 S 1 3

18

Se e f oo t no t e s a t e nd o f t a b l e .


31/342

t o

o

TABLE III. (cont.)

M

. . T y p i c a l h i g h - p o w e r o p e r a t i o n ( a p p r o x . )

a

Nom i na l . .

I n s t a l l a t i o n p e a k N u m b e r a n d ^ p

M ac h i ne u se S pec i a l capa b i l i t i e s t yp e o f c P eak P u l se Du t y E l ec t r on

l o c a t i o n e n e r g y

y K

b sou r ce E ner gy T

p

- .

,

M

s e c t i o n s c u r r e n t " r a t e f a c t o r p o w e r

1

' ( m A) ( M eV ) ( j i s ) ( Hz ) ( % ) ( kW)

19 Gi essen

6 5


M o n o - E p h o t o n s

( 8 - 3 5 M e V )

2 T W ( S ) 1 K

2 0 0

65 2

2 5 0

0 . 0 5 6 . 8 1 9

2 0 G l a s g o w

1 3 0 N u c l e a r p h y s i c s

n ( 0 1 0 M e V )

12 T W ( S )

3 K ( 20 ) 30 0

93 3 . S 150 0 . 0 5

14 20

2 1 H a m m e r s m i t h M R C 8 R a d i a t i o n p h y s i c s 1 T W 1 M ( 2 ) 2 5 7 2 3 0 0 0 . 0 6 0 . 1 2 1

22 Har we l l I 55


n ( 0 1 0 M e V )

7 T W ( S )

7 K (8)

SOO

30 2 . 0

2 0 0

0 . 0 4

5

2 2

2 3 H a r w e l l I I 1 3 6 N u c l e a r p h y s i c s n ( 0 - 3 0 M e V )

8 T W ( L )

4 K ( 2 0 ) 1 0 0 0

60 S.O

30 0 0 . 1 S

9 0

2 3

2 4 H e b r e w U n i v e r s i t y

( J e r u s a l e m )

8

P u l se r ad i o i y s i s

N a n o s e c o n d p u l s e s 1 T W 1 M 1 4 0 0

8

0 . 0 1

4 6 0

O.OOOS

1 24

2 5 H o k a i d o 4 5 N e u t r o n d i f f r a c t i o n

P u l se r ad i o i y s i s

3 T W ( S ) 100

4 5

3

2 0 0

0 . 0 6

5

2 5

26 Kar l s r uhe

2 2 F o o d p r e s e r v a t i o n 1 T W

1 K

100 16

4

3 0 0

0 . 1

2

2 6

2 7 K h a r k o v I

SOO

N u c l e a r p h y s i c s 2 7

28 Khar kov I I

2 0 0 0 P a r t i c l e p h y s i c s

4 9 T W

51 K ( 20 )

2 0 1 6 0 0

1.2

5 0 0 . 0 0 6

2 28

2 9 K y o t o 4 8 N e u t r o n p r o d u c t i o n

n ( 0 14 M eV ) 2 T W ( L )

2 K ( 10 )

5 0 0

25 4

180

0 . 0 7 1 0

2 9

3 0 L i v e r m o r e L L L 1 8 0 N u c l e a r p h y s i c s e ~ ( 1 0 1 8 0 M e V )


( 5 - 7 0 M e V )

n ( 0 3 0 M e V )

5 TW (S)

15 K ( 15 )

6 5 0

7 5

3 3 0 0

0 . 1 45 30

31 M ai nz

3 2 0 N u c l e a r p h y s i c s M o n o - E p h o t o n s

( 1 0 - 1 0 0 M e V )

N a n o s e c o n d p u l s e s

8 T W ( S )

8 K (2 5) 150

2 7 0 3

150

0 . 04 15

3 1

3 2 M a n c h e s t e r

( P a t e r s o n L a b s )

1 2 R a d i a t i o n b i o l o g y

R a d i a t i o n c h e m i s t r y

6 A in 10-ns pul se 1 TW 1 K (2 0) SOO 10 5

50 0 . 0 25 1 . 3

3 2

3 3 M I T B a t e s 4 0 0 N u c l e a r p h y s i c s L a r g e d u t y f a c t o r

H i g h - r e s . s p e c t r o m e t e r

2 2 T W ( S )

10 K ( 4 )

10

4 0 0

15 1250

1 . 8 60

3 3

3 4 M o n t e r e y N P G S

1 0 0 N u c l e a r p h y s i c s

3 T W

2 K 30

105 1

6 0 0 . 0 0 6

0 . 2 34

3 5 M o s c o w K u r c h a t o v N u c l e a r p h y s i c s N e u t r o n p r o d u c t i o n 6 T W

5 0 m s p u l s e a t 9 0 0 H z


32/342


N o m i n a l

N u m b e r a n d

R F

c


a


p e a k

M a c h i n e u s e

S pec i a l capab i l i t i e s

t ype o f

R F

c

P eak

E n e r g y

P u l se

D u t y

E l e c t r o n


S pec i a l capab i l i t i e s

s e c t i o n s '

5

s o u r c e

c u r r e n t

E n e r g y

T

P

r a t e f a c t o r

p o w e r

( M e V )

( m A )

( M e V )

(MS)

( H z )

(%)

( k W )

3 6 N a t i c k N A R A D C O M I S F o o d p r e s e r v a ti o n

M u l t i p l e b e a m p o r t s

2 T W ( S )

2 K (5)

s o o 1 0

5 180

0 . 0 9

5

36

R a d i a t i o n c h e m i s t r y

3 7 N B S ( W a s h i n g t o n ) 1 6 0


n ( 0 2 0 M e V )

9 T W ( L )

12 K 25 0 100 5

3 6 0

0 . 1 8 4 0

37

R a d i a t i o n s t a n d a r d s e * ( 1 0 - 4 0 M e V )

3 8 N P L ( L o n d o n )

2 2 R a d i a t i o n m e t r o l o g y

S A i n 5 - ns pu l se

2 T W

1 K ( 20 ) 75 0 15

3 . 2

2 4 0

0 . 0 7

8

3 8

3 9 N R C ( O t t a w a )

3 5

N u c l e a r

physics

N e u t r o n p r o d u c t i o n

4 T W ( S ) 1 K

2 5 0 3 5

3 . 2

1 8 0

0 . 06 5

3 9

4 0 N R L ( W a s h i n g t o n ) 6 0 R a d i a t i o n r e s e a r c h N e u t r o n p r o d u c t i o n 3 T W

3 K 4S 0 50

1 360

0 . 04 10

4 0

4 1 O a k R id g e O R E L A

178



4 T W ( L ) 4 K 1S 0 00 140

0 . 0 2 4

1 0 0 0

0 . 0 0 2 4 S O

4 1

4 2 O h i o S t a t e 6 P u l se r ad i o l y s i s N a n o s e c o n d p u l s e s 1 T W 1 M 325 6 0 . 0 1 5 5 0 0 . 0 0 0 6 4 2

4 3 O t s a y

2 3 0 0

P ar t i c l e phys i cs

e

+

( 0 1 . 3 G e V )

39 T W

39 K ( 20 , 25 ) 60

20 00 1 . 5 50

0 . 0 0 8

9 43

S t o r a g e r i n g s A C O ,

DCI

4 4 R a y c h e n n

17

P r o d u c t i r r a d i a t i o n

Hi gh cu r r en t 1 T W 1 K

1 1 0 0

10

6

2 0 0 0 . 1

10

4 4

( C o p e n h a g e n )

4 S R e n s s e l a e r 1 0 0 R a d i a t i o n r e s e a r c h

n ( 0 - 3 0 M e V ) 9 T W ( L ) 9 K ( 1 0 ) 3 0 0

4 5

4 . 5 720 0 . 32 S O

4 5

6 A in sho r t pu l se

4 6 R i o d e J a n e i r o

3 0


3 T W

1 A, 1 K

100 28

3 . 3

3 6 0 0 . 1

2 . 8 46

4 7 R I S p ( R o s k i l d e ) 1 4 R a d i a t i o n r e s e a r c h N a n o s e c o n d p u l s e s 1 T W 1 K ( 1 7 )

1 1 0 0

10

4

2 0 0

0 . 0 8 8 . 8

4 7

H i g h c u r r e n t

48 S ac l ay I 70


n ( 0 - 2 M e V ) 4 T W ( S )

4 K

100

7 0

2

SOO 0.1

7

4 8


( 7 - 4 0 M e V )

49 S ac l ay I I

6 0 0


M o n o - E p h o t o n s 3 0 T W ( S ) I S K ( 1 2 ) 2 5

4 0 0

2 0 1 0 0 0 2 . 0 2 0 0 4 9

( 2 0 - 1 2 0 M e V )

S O S t . B a r t h o l o m e w s

IS

R a d i a t i o n p h y s i c s

2 T W ( S ) 1 K ( 20 )

7 5 0

15

5

100 0 . 0 5 6

SO

( L o n d o n ) R a d i a t i o n b i o l o g y

51 S an Di ego I RT

1 0 0



4 T W ( L ) 4 K ( 40 )

7 0 0 6 0 4 . 5 1 8 0 0 . 0 8 3 5

51

P r o d u c t i r r a d i a t i o n

e

+

( 3 7 5 M e V )


( 3 - 7 5 M e V )

Se e foo tno te s a t e nd o f t a b le .


33/342

t o

T A B L EIII cont . )


N o m i n a l

i i i . l N u m b e r a n d

i n s t a l l a t i o n p e a K

M a c h i n e u s e

S p e c i a l c a p a b i l i t i e s t y p e o f

R t

c

P e a k P u l s e D u t y E l e c t r o .

l o c a t , o n

s e c t i o n s b

s o u r c e

c u r r e n t

t n e r 8 y T

P r a t e f a c t o r p o w e r

( M e V )

( m A ) ( M e V ) (lis) ( Hz ) ( % ) ( kW)

5 2 S . B a r b a r a E G & G 3 0

53 S ao P au l o US P 50

5 4 S a s k a t c h e w a n 2 5 0

5 5 S e n d a i ( T o h o k u ) 2 8 0

5 6 S t a n f o r d H E P L M k . I I I 1 2 0 0

5 7 S t a n f o r d H E P L 2 0 0 0

S C M ar k I I I

5 9 T o k a i J A E R I

6 0 T o k y o E T L

6 1 T o k y o I N S

6 2 T o k y o N E R L

6 3 T o r o n t o

6 4 W a r s a w

190

3 3

15

35

50

13






R a d i a t i o n t h e r a p y




R a d i a t i o n s t a n d a r d s

S o l i d - s t a t e p h y s i c s


N e u t r o n p h y s i c s

P u l se r ad i o l y s i s


P u l se r ad i o l y s i s


50 - ps pu l ses

n ( 0 - 1 5 0 M e V )

n ( 0 - 2 0 M e V )

e* ( up t o 1 G e V )

S u p e r c o n d u c t i n g l i n ac

D u t y f a c t o r = 1 0 0 %

P i o n t h e r a p y

e

+

( 0 1 5 G e V )

I n t e r l a c e d b e a m s

S P E A R s t o r a g e r i n g s

M u o n a n d m e s o n

b e a m s

P i c o s e c o n d p u l s e s

M o n o - E , p o l a r i z e d

p h o t o n s

P o l a r i z e d e l e c t r o n s

n ( 0 2 0 M e V )

1 8 0 s p e c t r o m e t e r

20 - ps pu l ses

e * ( 1 0 - 2 5 M e V )

n ( 0 2 0 M e V )


3 T W ( L )

2 TW

6 T W ( S )

5 T W ( S )

3 1 T W ( S )

8 S W ( L )

9 6 0 T W ( S )

5 T W ( S )

3 T W ( S )

1 TW (S)

2 T W ( S )

4 T W ( S )

2 T W

2 K

2 K

2 K ( 18 )

5 K ( 20 )

3 1 K ( 2 0 )

8 K ( 0 . 0 1 5 )

2 4 5 K ( 2 0 - 4 0 ) 7 0

5 K ( 20 )

2 K ( 17 )

1 K(6)

2 K ( 6 . 5 )

2 K ( 20 )

1 K

5 0 0 2 0 4 . 5 1 8 0 0 . 0 8 1 8 . 1 5 2

10 50

1

1 2 0 0 . 0 1 0 . 0 5

5 3

3 0 0

2 0 0 1 . 2 4 0 0 0 . 0 5 3 0 5 4

1 0 0 2 8 0 3 . 3 3 0 0 0 . 1 2 0

5S

30 120 0 1 . 3 120

0 . 0 1 6

6

56

0 . 1

2 0 0 0

CW

CW

1 0 0 .

2 0 0

57

7 0

2 1 5 0 0 1 6

3 6 0

0 . 0 6 8 0 0 5 8

3 5 0

2 0 0

2 0 0

200

4 0 0

800

100

3 0

13

3 5

150 0 . 0 3 11 59

60

2 1 . 5 0 . 0 0 2 6 0 . 0 7 6 1

200 0.08 6 62

2 4 0 0 . 0 8 4 1 2

3 0 0 0 . 0 9 9


34/342

N o m i n a l T y p i c a l h i g h - p o w e r o p e r a t i o n ( a p p r o x . )

3

I n s t a l l a t i o n p e a k N u m b e r a n d ^ p

M ach i ne u se S pec i a l capa b i l i t i e s t yp e o f c P eak _ P u l se Du t y E l ec t r o ;


K K

b s o u r c e E n e r g y T

p

- .

V

v s e c t i o n s c u r r e n t

v

r a t e f a c t o r p o w e r

K 6

' (MA) ( M e V ) (ms)

(H

z) ( % ) ( kW)

6 5 W h i t e S a n d s W S M R

4 8 N u c l e a r e f f e c t s


2 T W ( S ) 2 K ( 20 )

6 0 0

4 8

10 120

0 . 1 2

3 5

6 5

6 6 W i n f r i t h A E E I S

Rad i a t i o n r e sea r ch 1 T W ( S ) 1 K ( 10 )

2 0 0 1 4 4 . 5 2 0 0

0 . 0 9 2 . 5 6 6

6 7 Y a l e 7 0 N u c l e a r p h y s i c s

n ( 0 2 0 M e V )

S T W ( L )

7 0 0

4 0

4 . 5 2 5 0 O . U

30 67

6 8 Y e r e v a n

4 8 0 N u c l e a r p h y s i c s I t e r a t i v e a c c e l e r a t i o n

13 T W ( S ) 3 K ( 20 )

1 5 0 0 1 2 0

8

100

0 . 0 8 1 4 0 6 8

e

+

( 0 - 2 0 0 M e V )

( a ) P a r a m e t e r s s i m u l t a n e o u s l y a c h i e v a b l e h i g h e s t e l e c t r o n b e a m p o w e r u n d e r c o n t i n u o u s o p e r a t i o n .

( b ) T W = tr a v e l l i n g w a v e , S W = s t a n d i n g w a v e , S = S - b a n d , L = L - b a n d o p e r a t i n g f r e q u e n c y .

( c ) N u m b e r o f k l y s t r o n s ( K ) , m a g n e t r o n s ( M ) o r a m p l i t r o n s ( A ) . P e a k p o w e r p e r u n i t (M W ) g i v e n i n p a r e n t h e s e s .


35/342

I0

1

I 0

2

I 0

3

I 0

4

I 0

5

MAXIMUM ENERGY (MeV)

FIG.5. Beam power (kWj of representative electron linacs plotted against beam energy (MeV ).

The line represents the typical but arbitrary average current of 100 ^lA(corresponding to,

e.g., /

peak

= 100 mA, DF = 0.1%).

The parameters which most directly affect radiological safety are:

(a) Electro n beam energy E

0

(b) Average beam pow er P

( the product of E

0

and the average beam current I)

1

.

The most important derived quanti t ies of radiation protection, such as dose

rate or shielding thickness, are generally not simple functions of energy E

0

, and

the complete informat ion needed for radia t ion protect ion over a broad range of

energies requires an extensive set of tables or graphs.

Many qua ntit ies are relatively s impler fun ctio ns of energy wh en norma lized

to average beampower rath er tha n to average curre nt, and theref ore are so

pre sen ted in this ma nua l. A t a given energy E

0

, the dose rate or exposure rate is

directly proportional to average beam power P. The required shielding thickness

at a given distance, and for a given beam energy E

0

, is approxim ately propo r t ional

to the logarithm of average beam power.

1

The average pow er may be obtain ed from E

0

I because Eo, when specif ied in eV, is

numerical ly equal to the potent ia l d if ference (V) ef fect ively used to accelerate each part ic le .

Poten t ia l d if fer enc e (V ) t ime s current (A) is equal to pow er (W).

2 4


36/342

The beam is not continually accelerated but comes in short pulses of

typically T

P

=

1

- 3 /us du rati on . Where desired, T

P

can be made as short as 10 ps.

The pulse repe ti t ion rates may range betwee n 1 and 1440 Hz, bu t m ost are in the

range of 60 to 360 Hz. The du ty fa cto r DF is the fract ion of operating t im e during

wh ich th e linac is actually pro duc ing rad iatio n, which is generally in the range

1CT

4

to 10"

3

. It is th e prod uc t of pulse rep etiti on ra te p (in Hz) and pulse len gth

T

P

(in seconds):

DF = p Tp (1)

This small duty factor is a disadvantage in some research applications but is

un im po rtan t in the most com mo n applications such as radio thera py and ind ustr ial

radiog raphy . Special large-duty-factor and con tinuou sly operating (CW) accel-

erato rs have also bee n develop ed. Very short pulses (usually 5 10 ns) are used to

advantage in pulse radiolysis and neutral-particle spectrometry where precise t iming

of the reactions studied is crucial.

In radiological protection, the duty factor is important insofar as i t may

affect radia t ion measureme nts ; some measurements may be rendered comp lete ly

useless or even dangerously misleading by duty-factor effects . Any measurement

involving the counting of discrete events must be carefully evaluated to ensure

tha t these eff ec ts are ke pt small or pro pe rly co rrecte d f or . Geiger-Miiller and

proportional counters are particularly susceptible to saturation, owing to their

long dead times. Proce dures for correc tion are explained in Section 5.

REFERENCES TO SECTION 1

[1] See, for exam ple, papers in: LA PO STO LLE , P.M. , SEPT1ER, A.L. (Eds ) , Linear

Accelerators , North-Holland Publishing Co. , Amsterdam (1970) .

[2 ] See, for exam ple, papers in: Proc. 197 5 Part ic le Accelerator Conf . , Acceler ator Engineering

and Te chn olo gy, held in Washington, D C, 1 2 - 1 4 March 1975 , IEEE Trans . Nucl . Sci .

N S - 2 2 ( 1 9 7 5 ) .

[3] See, for exa mp le, papers in: Proc. IXth Int . Con f . High Energy Accelerators , held at

S tan ford L inear A cce lera tor C en ter , 2 - 7 May 1974 , C O N F -74 052 2 , U C -28-A cce lera tors

(TID-4500, 60th ed . ) , Nat ional Technical Information Service, Springf ie ld , Virginia (1974) .

[4 ] KA RZ M AR K, C.J ., PE RIN G, N.C. , Electro n linear accelerators for radiat ion therapy:

h i s tory , p r in c ip les an d con temp orary d eve lop men ts , Ph ys . Med . B io l . 18 (1973) 321 .

[5 ] AL M ON D, P.R. , Som e applicat ions of part ic le accelerators to cancer research and treatme nt ,

Ph ys . R ep . 17C 1 (19 75 ) .

[6 ] See, for exam ple, papers in: Proc. Co nf . Part ic le Acce lerators in Radiat ion Ther apy, held

at Los A lam os S c ien t i f i c Lab oratory , 2 - 5 Oct . 197 2 , U S A EC R ep . L A -5180-C , Tech n ica l

I n format ion C en ter , Oak R id ge , TN (1972) .

[7 ] BL Y, J .H. , High energy radiography: 1 - 3 0 MeV, Mater. Eval . (No v. 19 64 ) 1.

[8 ] See, for exam ple, papers in: Large Radiat ion Sou rces for Industria l Process ing (Proc.

S ymp . Mu n ich , 1969) , I A EA , V ien n a (1969) .

25


37/342

[9 ] See, for exa m ple, papers in: Radiat ion Preservat ion of Fo od (Proc. Sym p. Bo mb ay, 197 2) ,

I A E A , V i e n n a ( 1 9 7 3 ) .

[ 1 0 ] I N T E R N A T I O N A L A T O M I C E N E R G Y A G E N C Y , M an u al o n R a d i at i o n S t e r il i za t io n o f

Medical and Biological Materials , Technical Reports Series No.149, IAEA, Vienna (1973) .

[1 1] See, for exa mp le, papers in: BER M AN , B.L. , Ed. , Proc. Int . Con f . Pho tonucle ar R eact io ns

an d A p p l ica t ion s , A s ilomar , C a l ifornia , 2 6 - 3 0 M arch 1973 , Law ren ce L ivermore

Lab oratory an d U S A EC R ep . C ON F-7 303 01 , Of f ice o f I n form at ion S erv ices , Oak R id ge ,

T N ( 1 9 7 3 ) .

[1 2] FU LL ER , E.G. , "Ph otonu clear Phys ics 197 3: Where we are and how we got there",

Proc. Int . Conf . Photonuclear React ions and Applicat ions , As i lomar, Cal i fornia ,

2 6 - 3 0 March 1973 (BER M A N , B . L ., Ed . ) , Law ren ce L ivermore Lab oratory an d U S A EC

R ep . C O N F -73 03 01 , O f f ice o f In forma t ion S erv ices , Oak R id ge , TN (19 73 ) 1202 .

[1 3] See, for exa mp le, papers in: KIRK , W.T. , Ed. , Proc. 1975 Int . Sym p. Lepton and Pho ton

Interact ions at High Energies , held at Stanford Univers ity , 2127 Aug. 1975, Stanford

Linear Acce lerator Center, Stanfor d, CA (1 97 5) . ,

[ 1 4 ] C HOD OR O W, M., GI N Z TON , E . L . , HA N S E N , W.W., KY H L, R .L . , N EA L, R . B . ,

PA NO FS K Y, W .K.H. , Stanfor d high-energy linear accelerator (Mark III ), Rev. Sci .

I n s tru m. 27 (1 95 5) 134 .

[1 5] NE AL , R.B. , Gen . Ed. , DU PE N, D.W. , HO GG , H.A . , LOEW, G.A . , Eds , The Stanfor d

Tw o-Mi le A cce lera tor , Ben jamin , N ew Y ork (1968) .

[1 6 ] BOR GH I , R .P . , ELD R E D G E, A . L . , HELM, R . H. , LI S I N , A . F . , LOEW, G. A . , N EA L , R . B . ,

"Des ign, fabricat ion, ins tal lat ion , and performance of the accelerator s tructure", Ch. 6 ,

S tan ford Tw o-Mi le A cce lera tor (N EA L, R . B . , Ed . ) , Ben jamin , N ew Y ork (1968) .

[1 7 ] KNA PP, E.A. , KNAPP , B.C. , PO TTE R, J .M. , Standing wave high-energy l inear accelerator

structures, Rev. Sci. Instrum.

39

( 1 9 6 8 ) 9 7 9 .

[1 8 ] ON O , K., TA KA TA , K., S HI GE MU R A , N . , A sh ort e lec tron lin ac o f s id e -cou p led

structure with low inject io n voltage, Part. Acc el . 5 (1 97 3) 20 7.

26


38/342

2. RADIATION S AT ELECTRON

LINEAR ACCELERATOR INSTALLATIONS

2.1. Radiations anticipated and their quality factors

2.1.1. Types of radiations and their sources

The usefu l radiations at electron l inear accelerators are generally no t the

prima ry electron beams themselves bu t seconda ry beams. In mo st applications

the electrons are used to produce bremsstrahlung and the result ing penetrating

ph oto n beam s are those usefully em ploy ed, as in radiogra phy. In high-energy

research applications the use ful beam s may be of other typ es of secondary

par t ic les

2

, such as positrons and mesons.

The important exceptions to this generalization are the widely accepted uses

of diffuse electron beam s for radiation thera py, and f or research in nu clear

structure by means of high-energy electron scattering.

The dominant prompt radiation at al l energies is composed of photons

produced by bremsstrahlung in the materials which absorb the electron beam

energy. In fact , othe r prom pt radiations can be neglected com pletely unless the

energy exceeds th e threshold for ne utro n prod uct ion . Thresholds lie in the range

k

t h

= 613 MeV for most materials .

3

Above these energies, giant-reson ance

neutron production must be considered, both as a form of prompt radiation and

as related to induced activity.

At high energies , neutrons are produced in photonuclear reactions via the

quasi-deu teron e ffec t or in processes involving pi meson pro du ctio n. Althoug h

fewer in number than other types of secondary particles , these neutrons are quite

penetrating and in such installat ions may dominate the shielding requirements .

At yet higher energies , a forward-directed beam of mu mesons ( / j t ) is

produced which requires consideration.

The behaviour of these types of radiation as a function of electron energy

E

0

is qua litatively sket che d in Fig.6. In this figure, as in several figures and tables

in this man ual, 'absorbed dose rate ' or 'dose-equivalent rate ' are represented by q uan-

t i ties which can be represented by (Gy l T 'X k W -n r

2

) "

1

( ( r ad IT 'XkW-m"

2

)" ' ) ,

2

S ince these part ic les are prod uced alm ost ent irely by second ary pho ton s , rather

than by primary electro ns , they co uld prope rly be regarded as tert iary. This acco unts in part

for their lower f luen ces relat ive to the e lectro ns and photo ns . We shal l no t insis t on th is

dis t inct ion but refer to a l l types of prompt radiat ion, except the primary beam itself , as

'secondary' .

3

Th ere are s ome imp ortan t excep t ion s . For exam p le ,

2

H and

9

Be h ave an omalou s ly low

thresholds of k

t h

= 2 .2 3 and 1 .67 MeV , respec t ively . The abundant nucl id es

1 2

C (all organic

materials) and

I 6

0 (a ir , water) have h igh thresholds: 18 .72 and 1 5.67 Me V, respect ive ly .

27


39/342

Eg (MeV)

FIG.6. Dose-equivalent rates per unit primary bea m power, prod uced by various types of

'secondary' radiations from an electron target, as a function of primary beam energy, if no

shielding were present (qualitative). The width of the bands suggests the degree of variation

found, depending on such factors a s target material and thickness.

( r e m - h

_ 1

) ( k W - m ~

2

)

- 1

, etc. The quanti ty plotted is then equal to the dose-

equivalent rate that w ould be measured at 1 m fro m a target ont o which

a 1-kW elec tron be am is dire cted . The un it m

2

is inc lude d to suggest an inverse-

square depend ence on dis tance fro m the target fo r this typ e of radiation . An

inverse-square dependence is s tr ict ly true only for unshielded po

Documents

IAEA - Radiation Protection for LINACs