Short period wiggler Short period wiggler prototype for the CLIC prototype for the CLIC

damping ringdamping ring

Alexey BraginAlexey Bragin, Denis Gurov, Anatoly Utkin, Pavel , Denis Gurov, Anatoly Utkin, Pavel VoblyVobly

Budker Institute of Nuclear Physics, Novosibirsk, RussiaBudker Institute of Nuclear Physics, Novosibirsk, Russia

Mikko Karppinen, Remo Maccaferri, Jacky Mazet, Mikko Karppinen, Remo Maccaferri, Jacky Mazet, Stephan Russenschuk, Daniel SchoerlingStephan Russenschuk, Daniel Schoerling

CERN, Geneva, SwitzerlandCERN, Geneva, Switzerland

Main parameters of the wigglersMain parameters of the wigglers Period – 50 mmPeriod – 50 mm Total length of wigglersTotal length of wigglers Peak magnetic field – 2.5 TPeak magnetic field – 2.5 T Pole gap – 20 mmPole gap – 20 mm Beam aperture – 12 mmBeam aperture – 12 mm Total number of wigglers – 104Total number of wigglers – 104 The wigglerThe wiggler design has to be easy-to-design has to be easy-to-

produce, reliable and inexpensiveproduce, reliable and inexpensive

Overview of existing BINP wigglersOverview of existing BINP wigglers

YearMagnetic field, T

Number of poles

Gap, mm

Period, mm

Length, mm

Verticalaperture, mm

Elettra (Italy) 2002 3.7 (3.5) 45+4 16.5 64 1680 11

CLS (Canada) 2005 2.2 (2.0) 61+2 13.5 34 1120 9.5

DLS (UK) 2006 3.8 (3.5) 45+4 16.4 60 1544 10

Siberia-2 (Moscow)

2007 7.7 (7.5) 19+2 20.4 164 1836 14

CLS-2 (Canada)

2007 4.3 (4.0) 25+2 14 48 1000 9.5

LNLS (Brazil) 2009 4.1 31+4 18.4 60 1162 14

DLS-2 (UK) 2009 4.2 45+4 14 48 1304 13.8

ALBA-CELLS (Spain)

2010 2.2 117+2 12.6 30.2 1892 8.5

NbTi design of the short prototype for the CDRNbTi design of the short prototype for the CDR

Common NbTi wires (Cu/NbTi = >1) don’t meet Common NbTi wires (Cu/NbTi = >1) don’t meet the requirements of the CDR. Engineering current the requirements of the CDR. Engineering current of the NbTi wigglers at 4.2 K should be by a factor of the NbTi wigglers at 4.2 K should be by a factor of 1.3-1.5 higher if the wigglers would be made of of 1.3-1.5 higher if the wigglers would be made of common NbTi wires.common NbTi wires.

The NbTi wire, containing NbTi/Cu = 1.5/1, was The NbTi wire, containing NbTi/Cu = 1.5/1, was used in the BINP discussed here. The same wire used in the BINP discussed here. The same wire was used previously as shown in above table.was used previously as shown in above table.

The SC wire parameters areThe SC wire parameters are - Insulated diameter 0.92- Insulated diameter 0.92 mmmm - operational current 660 A at 6 T magnetic field in - operational current 660 A at 6 T magnetic field in

the coilsthe coils - number of filaments 375- number of filaments 375 - filament - filament 34 34 mm

Design principles, first prototypeDesign principles, first prototype The design principles are The design principles are

shown on the one half of the shown on the one half of the first prototype. first prototype.

The coils were wound around The coils were wound around the iron yoke without internal the iron yoke without internal wire splicing.wire splicing.

The neighbor coils are wound The neighbor coils are wound in opposite directions.in opposite directions.

Fiber glass plastic was placed Fiber glass plastic was placed between the coilsbetween the coils

Dry windingDry winding Epoxy compound impregnation Epoxy compound impregnation

at 15-20 bar pressure.at 15-20 bar pressure. Epoxy compound is Epoxy compound is epoxy – 50 mass partsepoxy – 50 mass parts AlAl22OO3 3 powder – 50 mass partspowder – 50 mass parts Active quench protection was Active quench protection was

used.used.

15+6 coils in one half15+6 coils in one half

Design principles, second prototypeDesign principles, second prototype

The same design, butThe same design, but

- the straight parts of the - the straight parts of the

coils were rounded coils were rounded

- the fiber glass plastic - the fiber glass plastic

was removed.was removed.

High heat capacity GdHigh heat capacity Gd22OO22S S

powder was added to the powder was added to the

epoxy compound.epoxy compound.

Its quantity is 10% of the Its quantity is 10% of the

total mass of the compound.total mass of the compound.

Magnetic fields calculationsMagnetic fields calculations1

MN

MX

X

Y Z

.193E-03

22.2

2.452.55

3.55

5.59

APR 29 201014:06:06

STEP=1SUB =1TIME=1BSUM (AVG)RSYS=0SMN =.193E-03SMX =8.308

ANSYS 2D calculations and MERMAID 2D and 3D calculations

Magnetic fields in the working volume. ANSYS 2D.

Second prototype. Really wound coils are shown.

Maximal magnetic fields are in the central coil at round parts.

MERMAID 3D.

Stability and Protection of the wigglerStability and Protection of the wiggler Stability parameters of the considered wiggler design are low Stability parameters of the considered wiggler design are low

due to less amount the copper stabilizer and high Iop/Ic ratio. due to less amount the copper stabilizer and high Iop/Ic ratio. These factors cause high risk of a degradation.These factors cause high risk of a degradation.

To increase stability of the wiggler To increase stability of the wiggler

- epoxy compound with fine powder is used- epoxy compound with fine powder is used

- all possibilities to increase Ic should be used- all possibilities to increase Ic should be used

Active protection is Active protection is

considered as a main considered as a main

method of the wigglermethod of the wiggler

protection.protection.

It was tested in the first It was tested in the first

prototype.prototype.

Epoxy impregnationEpoxy impregnation

One half of the wiggler is

Prepared for the impregnation.

The half of the wiggler after impregnation. The Gd2O2S powder is seemed to be completely precipitated on the bottom.

Four wiggler parts were successfully

impregnated by this way.

Impregnation area. Autoclave presses the impregnated wiggler by 1.5-2 MPa at 90 C.

Test results of the first prototypeTest results of the first prototype

The first prototype wasThe first prototype wastested three times. tested three times. A strong degradation wasA strong degradation wasobserved.observed.The maximal current was The maximal current was 450 A at 1.9 K (CERN) that450 A at 1.9 K (CERN) thatis too far from theis too far from theoperational 660 A.operational 660 A.

The main reason of the The main reason of the degradation was the glassdegradation was the glassfiber spacers due to muchfiber spacers due to muchdifference between the difference between the thermal contraction of thethermal contraction of thespacers and the iron.spacers and the iron.ANSYS calculations have ANSYS calculations have Proved this conclusion.Proved this conclusion.

1

MN

MX

XY

Z

511982

.733E+08.146E+09

.219E+09.292E+09

.365E+09.437E+09

.510E+09.583E+09

NODAL SOLUTION

STEP=1SUB =1TIME=1SEQV (AVG)DMX =.283E-03SMN =511982SMX =.583E+09

Test results of the second prototypeTest results of the second prototype

One half of the second One half of the second prototype was tested prototype was tested separately with iron plate. separately with iron plate.

Operational current of 660 A Operational current of 660 A and critical current of 700 A and critical current of 700 A were achieved.were achieved.

In the second prototype test In the second prototype test operational current of 660 A operational current of 660 A and critical current of 693 A and critical current of 693 A of the second half were of the second half were achieved.achieved.

High ramping rate is seemed High ramping rate is seemed to be the main reason of to be the main reason of much training quenches.much training quenches.

(5 times higher)(5 times higher)

One half training history

Second prototype training history

Test results of the second prototype, conclusionsTest results of the second prototype, conclusions 1. Operational current of 660 A was 1. Operational current of 660 A was

achieved – the main result.achieved – the main result. 2. Training quench statistics shows:2. Training quench statistics shows: - 88% of the quenches of the one - 88% of the quenches of the one

half test were in the half test were in the 6A coil.6A coil. - 56% of the quenches of the - 56% of the quenches of the

wiggler test were in the wiggler test were in the 6B coil. The 6A and 6B coils 6B coil. The 6A and 6B coils

contains ½ turns of central coil.contains ½ turns of central coil. - the central coils (4A, 4B) induced - the central coils (4A, 4B) induced

the training quenches.the training quenches.

3. The influence of the high ramping rate was not understood during the 3. The influence of the high ramping rate was not understood during the wiggler test. It was by a factor of 5 higher than in the one half test, so a wiggler test. It was by a factor of 5 higher than in the one half test, so a heat generation due to AC loss was by a factor of 25 higher.heat generation due to AC loss was by a factor of 25 higher.

4. The depth of grooves in the iron, where the coils are wound, is not 4. The depth of grooves in the iron, where the coils are wound, is not optimal. SO, in the conducted tests the maximal magnetic field was optimal. SO, in the conducted tests the maximal magnetic field was about 2.2 T in the working volume. Nevertheless, it does not affect the about 2.2 T in the working volume. Nevertheless, it does not affect the maximal field inside the coils. maximal field inside the coils.

Outer turns of 6A and 6B coils are not Outer turns of 6A and 6B coils are not backed by iron walls as in 2A and 2B.backed by iron walls as in 2A and 2B.

Possible improvements of the NbTi designPossible improvements of the NbTi design

1. Removing of 2 mm of 1. Removing of 2 mm of iron at the round parts iron at the round parts will increase the critical will increase the critical current up to 730 A. It will current up to 730 A. It will improve the stability.improve the stability.

Properties TiB2 SiC Al2O3 BN AlN

Cryst. structure Hex. Hex. Hex. Hex. Hex.

Density, g/cm3 4.52 3.19-3.21 3.9-4.0 2.25 3.25-3.3

, 10-6 1/K 4.6-8.1 4.63-4.7 3.6-9.5 0.8-7.5 53

E, GPa 500 350-490 380-490 90 350-380

t, GPa 1.29 0.4-1.7 0.2-6.5 1.2-1.38 3.5-7.0

Tm, K 3253 2873-2970 2312 3253 2703

2. Taking BN as a filling powder for 2. Taking BN as a filling powder for the epoxy compound is more the epoxy compound is more advantageous according the shown advantageous according the shown table and plots.table and plots.

ConclusionsConclusions The short prototype of the wiggler were tested up to The short prototype of the wiggler were tested up to

the critical current that prove the possibility to use the critical current that prove the possibility to use NbTi wiggler design at 4.3 K for the CDR.NbTi wiggler design at 4.3 K for the CDR.

The developed technology of the epoxy impregnation The developed technology of the epoxy impregnation seems reliable and effective.seems reliable and effective.

Improvements of the current design are shown which Improvements of the current design are shown which should increase stability of the wiggler.should increase stability of the wiggler.

The reasons of premature quenches of the first and The reasons of premature quenches of the first and second prototypes are understood and discussed how second prototypes are understood and discussed how can they be minimized.can they be minimized.