LXe calibrations, PMT tests, cryostat construction

February 9th 200511

LXe calibrations, PMT tests, cryostat construction

1. Alpha sources on wires

2. 9 MeV from neutron capture in Nickel

3. 0

4. further calibration methods ?

5. PMTs tests

6. Cryostat status

Calibrations

22

1) Alpha sources spots on wires

• Sorces at different distances seen by each PMT: unique feature• Made at Genova INFN• electrodeposited ( solution) on a gold-plated W wire

• 0.5 mm spots 12.4 cm apart (2 PMTs)• Wire thickness: 50 (alpha range ~40 )• Wire suspended with springs

–Wires A,B = 100 Bq/source (LP front face)–Wires C,D = 30 Bq/source (LP back face)

•A Czech Republic firm can provide a suitable wire in which Am on foils is attached to wires by thermocompression

LP Front face Lateral face

33

44

February 9th 200555

•The ring radius depends on the Rauleigh scattering length

•The best value for reproducing the radius is 20 cm

•In contrast with previous estimates!

•Reflection ? ...we must improve the simulation and detector understanding

66

Small displacement of the two front wires

LXe GXe

77

PMT alpha direction

88

Charge vs Cos in LXeFront Face

Data MC

99

LXe/MC

New PMTs

Old PMTs4 front sources

1010

LXe/MC

After applying QEs

4 front sources

1111

70 kHz photons with E>5 MeV from muon radiative decay @ R() 3x10**7. Total sources rate O(15 KBq @ 5 MeV)

Towards the final calorimeter

1212

Po half-life=138 days

Trigger was changed several times …

February 9th 20051313

AMERICIUM WIRE-SOURCES

World-wide search (from 2003...):

• ISOTRAK-AEA TECHNOLOGY • ISOTOPE PRODUCTS• LEA-CERCA• NORTH AMERICAN SCIENTIFIC• FRAMATOME• ETC.

all of them refused to consider this custom-made product....! too difficult, too long development, too expensive, etc.

Finally: found a factory, Czech republic, Pragueworking on ionization smoke detectors and electrostatic charge eliminators

(8 people.....)

accepted to perform a R&D for our special request. UP and DOWN SUCCESS !:

Production method by “thermocompression”. Liquid Nitrogen tests at ENEA.

VERY IMPORTANT FOR FUTURE CRYOGENIC LIQUID DETECTORSunique feature !


SPECIFICATIONS FOR THE PRODUCTION OF SEVERAL Am WIRE-SOURCES

AND SEVERAL Am DISK-SOURCES January 5th 2005

The wire sources should be produced according to the 3 model drawings “final calorimeter” (15 wires), “large prototype” (8 wires), Pisa device (2 wires). Final calorimeter: 15 wires, 5 dot-sources per wire,Large prototype: 10 wires, 2 dot-sources per wire, Pisa device: 2 wires, a single dot source The Am dots should be mounted by thermocompression on a gold plated steel or tungsten wire of diameter 100 m. The resulting wire diameter, after the source mounting, should be < 200 m. The source surface should be as smooth and regular as possible. The dot sources should be covered by a protective gold layer 1.5 m thick. The activity of each Am dot should be about 200 Bq with a tolerance 25%. Each dot should have a linear dimension < 2 mm. The position of each dot on the wire should be precise within 1 mm. A reference mark (non radioactive !) should be mounted on one side of the wire only; the mark (perhaps a gold layer fixed by thermocompression) should be easily visible. The wires must be shipped without damaging them; each wire could perhaps be mounted on a thin plastic rod or wrapped around a large diameter spool. The 25 disk-sources should be gold plated disks of diameter 5 mm and have an activity of 500 Bq per source. Each source should be covered by a protective gold layer 1.5 m.

SPECITICATIONSAND CONTRACT

FOR THE PRODUCTION OF Am WIRE-SOURCES AND

OF Am DISK-SOURCESReady: end of March 2005

(TOTAL ACTIVITY < 40 kBq)

Each dot-source: small radioative foil fixed on wire by

“thermocompression”

TESTED AT NITROGEN TEMPERATUREAT THE ENEA LAB. IN ROME. OK !

NEEDED FROM PSI:•Authorization of nuclear security for products•Authorization for import of radioactive sources•Auhorization for production of detectors using radioactive sources


Wire of 100 micron diameterMaterial: gold plated steel or tungsten Total length 150 cmSpacing of dot-sources 12.4 cmLinear dimension of dots 1-2 mmActivity 200 Bq per dot

150 cm total wire length

Am dots

12.4 cm distance between Am dots

Reference Mark

20.0 cm distance between Mark and First Dot

Central Dot

WIRE SOURCES FOR FINAL CALORIMETER15 WIRES, 5 DOT-SOURCES PER WIRE


Wire of 100 micron diameterMaterial: gold plated steel or tungsten Total length 150 cmSpacing of dot-sources 12.4 cmLinear dimension of dots 1-2 mmActivity 200 Bq per dot


Am dots

12.4 cm distance between Am dots

Reference Mark

20.0 cm distance between Mark and First Dot

Wire centre

WIRE SOURCES FOR LARGE PROTOTYPE10 WIRES, 2 DOT-SOURCES PER WIRE


Wire of 100 micron diameterMaterial: gold plated steel or tungsten Total length 50 cmCentral dot-source Linear dimension of dots 1-2 mmDot Activity 200 Bq


Reference Mark

20.0 cm distance between Mark and Dot

Central Am Dot

WIRE SOURCES FOR PISA DEVICE2 WIRES, 1 DOT-SOURCE PER WIRE



rather narrowenergy-spectra

possible mounting on special

supports and screws


Will it be possible to use them @ beam on?Will it be possible to use them @ beam on?


2) 9 MeV gamma line from neutron capture 2) 9 MeV gamma line from neutron capture on Nickelon Nickel:Experimental set-upExperimental set-up

- Am-Be source Am-Be source (20000 n/s);(20000 n/s);

- Polyethylene;Polyethylene;

- Nickel platesNickel plates 30 x 30 cm30 x 30 cm22 ((0.5 cm0.5 cm and and 0.25 cm0.25 cm thickness)thickness) - 20 x 20 x 36 cm20 x 20 x 36 cm33 NaI detectorNaI detector

-MCAMCA ORTECORTEC (2048 channels)(2048 channels)

- NIM electronics.NIM electronics.


γ-line from n-capture on Ni, I, Al, H2; natural radioactivity Tl, K; Am/Be source

Am/Be4.4 MeV &1st escape

I6.8 Mev

Al7.7 MeV

Ni9 MeV

Ni8.54 MeV &1st escape

H2

2.2 MeV

Tl2.6 MeV

Black: Am/Be source and 1 cm Ni Red: no Am/Be sourceGreen: no Am-Be source, no Ni(Gotta Beam on)

K1.46 MeV


9 MeV Nickel γ-line

NaI 20 x 20 x 36 cmNaI 20 x 20 x 36 cm33

neutron generator (Pavia ?)

• Intensities from 106 n/s to 108 n/s• Typical pulse rate and pulse width 10 Hz and 1 μs • Time separation of direct from delayed reactions• Single pulse mode

THERMAL NEUTRON CAPTURE ON NICKEL

Potentialities :• switchable on-off• frequent (s, m,...) stability checks• system out of the calorimeter• Ni and Xe, prompt and delayed signals• probably: visible signal at full beam intensity• time reference

Open problems:• monitoring from calorimeter back• only at one location ?• some dispersed neutrons and radioactivity• test of the method at high beam intensity• useful test with the “large prototype” (already foreseen in April, with Am/Be source)

D + 2H 3He + n Q = 3.27 MeV

D + 3H 4He + n Q = 17.59 MeV

Polyethylene

0.25 cm Nickel plate

3 cm 20 cm


PossibilitiesPOLY POLYPOLY

Am/Be

0.25 cm Nickel

n

POLY POLY

3 cm polyethylene

NaI


3)0 calibration…

Target

Anti Counter

up

tilt

down

Support structure: straightly up and downTilt mechanism at every height for NaI front to face target direction.

target

00

• Proton beam: 1.8mA

• Pion Rate: 2x107 -/sec

• Collimate: 2PMTs x 2PMTs ~ 150cm2

(1 position)

• 2 /sec

• # of PMTs on incident face: 216 PMTs (54 positions)

• required: 30,000 evts/position

• takes 30,000 x 54 / 2 =

810,000sec~ 10 days

How often can it be How often can it be performed?performed?


3) Further calibration methods... 500 KV PROTON ACCELERATOAND LITIUM TARGET FOR A

17.6 MEV GAMMA LINE

Potentialities :• a unique nuclear reaction with a high energy -line (10 KeV)• obtainable : 106 /s (isotropic) at 440 KeV resonance (Ip 50 A)• from LiF target at COBRA center; ’s on the whole cal. entrance face • energy and position calibration; shower properties; all over LXe cal.• possibly: rather frequent use

Open problems:• compatibility with normal beam and target ?• project for easiness of target-tube mounting• accelerator/COBRA, which position and distance ? • p-beam divergence and protons on target; p29 MeV/c • 500 KeV and criticality of an air-insulated accelerator• is a post-acceleration possible ?

[P.R. 73, 666 (1948), N.P. 21 1 (1960), Zeitschrift f. Physik A351 229 (1995)] 3

7Li (p,)48Be


Previously used...


37Li (p,)4

8Be

resonant at Ep= 440 keV =14 keV peak = 5 mbE0 = 17.6 MeVE1 = 14.6

6.1Bpeak 0/(0+ 1)= 0.720.07

NaI 12”x12” spectrum

1

0

Crystal Ball Data


511B (p,)6

12C

lower proton energy !lower rate at 50 A !!

A further interesting possibility...Cecil et al. NP A539 75 (1992)10x10 cm NaI crystal

resonant at Ep= 163 keV= 7 keVE0 = 16.1 MeV peak = 5.5 bE1 = 11.7 + 4.4 peak = 152 b

750 0/s (isotropic) 20.000 1/s for Ip 50 A


NOW: GLAST SPACE EXPERIMENTCRYSTAL CALORIMETER CALIBRATION

It is the old VDG of the Crystal Box experiment ! !they have some problems: old device, max. VDG p-energy is 400 KeVout of resonance: -rate reduced by factor 5000 How can we get one such device ?? We are exploring several possibilities...

180 cm target-pipe


rails

cockroft

focusing elements(magnetic or electrostatic ?)

Cal. calibration from the target position, monitoring at the cal. back

at the cal. back the proton motion in the COBRA field must be be studied


proton MC trajectoriesEp 440 keV 28 MeV/c !!

Z(cm)

X(cm)

Y(cm) the protons are not reflected back by the varying magnetic field

Θ ~ 8 giroradius < 12 cm


Z(cm)X(cm)

Y(cm)

ρ ~0.8cm

Plane Z = 0 cm

Θ ~ 0.5 giroradius < 1 cm


KEEP MEG UNDER CONTROL

PARTICULARLY AT HIGH (AND VARIABLE) BEAM INTENSITIES.........

• frequent checks of calorimeter energy scale, linearity and stability• checks of LXe optical properties • energy resolution and spacial resolution• shower properties• at the right energy ( 53 MeV), but also at other energies.....

no single calibration method has all the required characteristics

use complementary (and redundant) methods, make the best use of their intrinsic properties

emphasize the reliability of our experiment

BR e ~10-13 Beam Intensity~5 107 /s


5) PMT tests

<Q> = 50 pC

F18, TB type F0, 6041 (old)

<Q> = 87 pC

PMT in LP, LED pulsed (@ 1 khz)


10 Khz

<Q> = 50 pC

TB 6041

<Q> = 87 pC

photocathode saturation effect


50 Khz

<Q> = 50 pC

TB 6041

<Q> = 87 pC

photocathode saturation effect


100 Khz

<Q> = 50 pC

TB 6041

<Q> = 87 pC

Gain non linearity


6041

= 115 s

Anode current should be < 0.5 A


TB

Lower photocathode resistivity (ZA much better)


Zener Diodes on PMT Base

4242

Linearity much improved

presently installed

PMT with Zener

T=-108ºC

4343

But … Zener problem at low temperature

•Positive pulses with total positive charge are seen! (rate ~300 Hz @ V>20 mV)•The problem is present ONLY at liquid Xe temperature: disappears during warm-up •The pulse is not present when the Zener diodes are removed

4444

Several Zener diode types tried

Seller Brand Package

Distrelec FairChild Glass

Farnell Phillips plastic

RS On semicond plastic

RS Phillips Ceramic

Original ... plastic

RS Vishay sinter gl.

4545

Results: FairChild

68+75 5 Hz

75+75 200 Hz

(75//75)x2 3 Hz


R9288 base with low pass filter

Optimum resistance will be something around 100KOhm

Low pass filter is built in by adding resistors serial to Zener

If the resistance is too small, filtering will not work. With too large resistance, the effect of Zener will be little

under high rate BG environment


Low pass filter in PMT base @ Astro-E2 HXDPMT base with Zener diode and

low pass filter is adopted in Astro-E2 Hard X-ray Detector. (HXD)

Fifth Japanese space X-ray observatoryPMT+BGOHigh counting rateHXD will be cooled downed to –30 °C

Zener is used in this base circuit and low pass filter is built in because of the noise from Zener. Various tests have been performed with this base and its good performance was confirmed so far.


PMT Test using the base with Low Pass filter

Type Z Type ZR


Chamber Set Up

Type ZR

Gas xenon

Alpha source LED

Type Z

Upper PMT temp.

~ - 85 °C

Lower PMT temp.

~ - 100 °C

HV=800V for both PMTsSame interstage volt., same current between 2 PMTs


Oscilloscope SnapshotType Z

Type ZR

Yasuko HISAMATSU MEG Collaboration Meeting Feb. 2005

No noise was observed!!

Noise from Zener

Alpha event


We have an alternative; active base with MOS-FET

Adopted in the πβ experiment MOS-FET is operational in 165K

If the base Type ZR doesn’t work…


When a solution is found

Start testing PMTs: 300-400 at Pisa (Cryo facility) and 600-700 at PSI (LP)


6) Cryostat: designs ready; tenders and procurements organization

Tenders have been organized in three parts:1. Conventional part2. Cold and warm windows3. Purchasing of the cold sealing 4. PMTs supporting structure The tender procedure has been completed for the conventional part. SIMIC has won the tender for the best price and for other reasons.This company is going to purchase a low magnetic permeability

stainless steel (<1.008) and will perform the cold test at the company. We visited the company to warn them about the project difficulty, remarking our requirements in term of level of cleanness and tightness written in the tender technical specification.

The company, if it will receive in time the cold and warm window and the cold sealing, estimated a fabrication time of 10th month.


SIMIC profile in cryogenics application

http://www.simic.it/eng/home.htm


Cold and warm windows

• FEA studies are in progress.• Honeycomb structure has been discussed with manufacturing companies

We are trying to subdivide the fabrication and qualification of the window to be able to maintain the cost as low as possible

We have separated the following activities.

• Mechanical test ( Mech. Dept Univ of Pisa)• Test box and welded parts (Mechanical design INFN (Pisa) manufacturing with proper company)• Tooling and molds are going to be designed by INFN (Pisa)• Honeycomb structure (Composite aerospace company)


FEA studies are in progress

0

0,00005

0,0001

0,00015

0,0002

0,00025

0,0003

0,00035

0,0004

0,00045

0,0005

0,0003 0,0004 0,0006 0,001

thickness ( m )

max

dis

plac

emen

t ( m

)

incastro max displ-thickness cerniera max displ-thickness

0

20000000

40000000

60000000

80000000

100000000

120000000

140000000

160000000

180000000

200000000

0,0003 0,0004 0,0006 0,001

thickness ( m )

max

prin

cipa

l ( P

a )

cerniera max princ-thickness membrane theory

0

20000000

40000000

60000000

80000000

100000000

120000000

140000000

160000000

180000000

200000000

0,0003 0,0004 0,0006 0,001

thickness ( m )

max

prin

cipa

l ( P

a )

Incastro max princ-thickness membrane theory


Honeycomb structure discussed with manufacturing company

Internal welded foil .3 mm or less welded on externalFrame necessary to test the window prior the final welding on the cryostat body.

Bolted area

This area is reinforced

Honeycomb structureTwo facing of .7 mm CFRP.(intermediate high module CF withEpoxy space approved)Core aluminum honeycombperforated


Honeycomb structure has been discussed with manufacturing company

Precision must been obtained on this side for this reason the honeycomb must rest on the mold on this side

Using thin facing material makes difficult to obtain high tolerance, even if we use a flex core material, not available in perforated aluminum.

This area is reinforced


Cold joints: interaction with the factory

Modification of bolts position and number

We asked non-magnetic seal


Pisa 30-December-2004Cold joints


PMTs supporting structure design


Some issues recently reviewed

•Detailed drawings of internal attachments

•Windows area dimensions reviewed.

•Superinsulation required to the company

•Electro polishing of internal surfaces

•Outer vessel isolated from the base. (A G10 plate will be placed under the cryostat legs)

•Reviewed the height of all components

•Metallic o-rings to be fixed in the vertical position

•Guiding pins needs to be added on the cold and on the warm flange to avoiding that the studs are hitting the contact surface of the o-ring on the covers


Calorimeter schedule

2005


Neutron measurements Neutron measurements statusstatus

44

Device Location Beam type Average Beam int.

(mA)

Thermal n flux

(cm- 2 s- 1)

Non thermal n flux

(cm- 2 s- 1) NaI 1 Positive 1.5 3.5 – 4 unknown Pisa LiI + Bonner 2 Positive 1.67 6 ~ 25 He3 1-2 Positive 1.5 6- 7 unknown Tokyo

He3+ Bonner 4 Positive 1.8 2 ~ 12

Documents

LXe calibrations, PMT tests, cryostat construction