1 Tetsuhiko Yorita JASRI/SPring-8 Acc. Div. SPring-8 Vacuum System Contents - Outline of Vacuum...
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Transcript of 1 Tetsuhiko Yorita JASRI/SPring-8 Acc. Div. SPring-8 Vacuum System Contents - Outline of Vacuum...
1
Tetsuhiko YoritaJASRI/SPring-8 Acc. Div.
SPring-8 Vacuum System
Contents
- Outline of Vacuum system- Pressure behavior- Some topics
2
100 mA, 8 GeVCircumference : 1436m, 44 normal cells + 4 Long Straight Sections
Accelerator Complex of SPring-8
Storage Ring
BoosterSynchrotron
Linac
3
e-
length of one cell = 24m (excluding ID) 3 Straight Section Chambers (SC1-3), 2 Bending Magnet Chambers (BM1,2), Absorbers (CR1,2,AB2,3,4)
Normal cell
4
Beam Chamber : Ellipse 40mm(vert.)*70mm(hori.)Slot Height : 10mm(14mm) for SC, 12.5mm for BM
Material: Al Alloy A6063-T5 (special extrusion in Ar+O2)
Straight Section ChamberSC1-3
BendingMagnetChamberBM1,2
Chamber cross sectionSC1SC2SC3 BM1BM2
e-
5
AbsorbersCR1
CR2
AB3
AB4
AB2 AB1
crotch (CR1,2)
absorber (AB3,4)
crotch(CR1,2) absorber(AB3,4)SR power (100mA) 5.8 kW (370 W/mm2) 4 kW (50 W/mm2)max. temperature 417 oC 215 oC
max. thermal stress 37 kg/mm2 28 kg/mm2
Allowable thermal cycles 7x104 1x106
Material : Glid-Cop
6
SC1-3, BM1,2 - Distributed NEG Pump (DNP) *26m (St707/CTAM/30D)
- Distributed Ion Pump (DIP) *5m
CR1,2 & AB3,4 - Lumped NEG Pump (LNP) *4 (St707 WP1250 *20)
- Sputter Ion Pump (SIP) *4
Pumps
LNP
SIP
LNP
pumping speed / cell for CO : 6x103 L/sec
for H2 : 1.6x104 L/sec
DNP
7
10-7
10-6
10-5
10-4
10-3
0.1 1 10 100 1000 104
average_ab3 (Pa/A)average_ab4 (Pa/A)average_cr1 (Pa/A)average_cr2 (Pa/A)average_sc1(Pa/A)
ab3ab4cr1cr2sc1
P/I
(P
a/A
)
dose(Ahr)
- P/I decrease with Dx
(x ~ -2/3) - Neither AB nor CR decrease with dose 10~1000 Ahr. - Pressure readings of AB and CR have error due to irradiation. --> BA gauges and cables were shielded.
Pressure rise by SR (P/I) vs. dose
SC1CR1CR2 AB3AB4
8
4 10-9
5 10-9
6 10-9
7 10-9
8 10-9
9 10-9
10-8
2 10-8
3 10-8
4 10-8
0.1 1 10 100 1000 104
TD_normal_ab3 (Pa)TD_normal_ab4 (Pa)TD_normal_cr1 (Pa)TD_normal_cr2 (Pa)TD_normal_sc1 (Pa)
pre
ss
ure
(P
a)
dose(Ahr)
dose(Ahr)Aug/1997:11
1998:661999:2852000:626
2001:10142002:13752003:1769
Beam current = 0mA
Pressure of thermal desorption
NEG reactivation in whole ring - In 1997 (dose 11 Ahr) -->effective - In 1998 (dose 66 Ahr) NEG reactivation in half of ring - In 2001 (dose 1014 Ahr) Recently base pressure is almost constant.
SC1CR1CR2 AB3AB4
9
10-3
10-2
10-1
100
101
102
10-2
10-1
100
101
102
103
104
lifetime*I(Ah)
lifet
ime*
I(A
hr)
dose(Ahr)
Dec/31/1997=29 Ahr /1998=146 /1999=426 /2000=764
/2001=1183 /2002=1578 /2003=1957
NEG reactivation in1997 summer
Replacement of 30mLSS
Replacementof ID17
Lifetime (multi bunch, ID gap : full open)
- Lifetime by gas scattering
> 600 hrs (calculation)
100mA, CO=30%
- Actual Lifetime ~200hrs
lifetime by gas scattering
is not primal.
10
Absorber at RF sectionleaked cooling water (gas) There is a possibility thatSR, water and dissolvedoxygen corroded Cu. Normal absorbers arenot so serious,because of different water serieswith less oxygen.
Corrosion with water and SR(RF-AB)
11
0.7t
Leakage due to the melting of chamberby aborted electrons
10mm
Injection chamber - narrowest aperture - thin chamber wall of stainless steel - some dispersion at low emi. opt.
Most of aborted electrons hit the wall and melt it
Injection chamber
cross sectionsof chamber wall
12
Electro-Magnetic Showerbremsstrahlung e+e- pair creation
&
0.1mm
heat load markis broader thanbeam size of7x290m2
Leakage due to the melting of chamberby aborted electrons (Cont’)
EM shower density depends on Z.
To avoid the melt, electron dumper made of Al with low Z has been installed
cascade of
13
Beam Fluctuation
S. Matsui, et al.Jpn. J. Appl. Phys.Vol. 42 (2003) pp.L338
Eddy Current madeby Q-mag. field kicksthe electron beam.
Typical Chamber Vibration (AB2)
Beam Fluctuationdue to Chamber Vibration
14
Chamber Vibration @AB2
Beam Fluctuation
Reduction withadditional supports
Beam Fluctuationdue to Chamber Vibration (Cont’)
15
Appendix A : ImpedanceBellows and gate valves
- RF finger in bellows CuBe(C1720)
Flange
- RF contact: CuBe(C1720)
Joint part of beam chamber
- Step < 0.5 mm
- Gap < 0.2 mm
Connection between
different cross sections
- Transition angle < 5 ~ 10 deg
16
beam size 10x390m2
-->7x290m2
ID section
Appendix B-1:low emittance operationNov. 2002 ~ Oct. 2003Sep. 2005 ~
17
IDsection
Appendix B-2:aborted electronbehavior