Superconducting magnets for SR generation in Budker INP: the status of works
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Transcript of Superconducting magnets for SR generation in Budker INP: the status of works
RUPAC-2006, Novosibirsk 1
Superconducting magnets for SR generation in Budker
INP: the status of works
N.A. Mezentsev
Budker INP, Novosibirsk, Russia
RUPAC-2006, Novosibirsk 2
In Budker INP of Siberian Branch of Russian Academy of Science already more than 25 years there is an activity on creation of superconducting special magnets for generation synchrotron radiation, such as superconducting 3-pole magnets – «shifters», superconducting multipole magnets – «wiggler» and bending superconducting magnets – «superbends».
Spectral characteristics of Synchrotron Radiation (SR) from bending magnet are determined by two parameters: electron energy E and magnetic field B, с~E2B.
There are two ways how to make a spectrum harder : •to increase electron energy •to increase magnetic field in radiation point.
The first way of increase of hardness has many advantages, but demands big material and manpower resources, while the second way is cheap enough and rather simple at use of insertion devices like
•superconducting wave length shifters•superconducting wigglers •superconducting high field bending magnets (superbends).
INTRODUCTION
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Year
Magnetic field, T Max/
normal
Magnetic gap, mm
Magnetic length,
mm
Vertical aperture,
mm
Electron energy
GeV
Liquid helium consumption, LHe liter/hour
WLS for Siberia-1 (Moscow)
1985
5.8 (4.5)
32
350
22
0.45
2-2.5
WLS for PLS (Korea)
1995
7.68 (7.5)
48
800
26
2
1.5-2
WLS for LSU-CAMD (USA)
1998
7.55 (7.0)
51
972
32
1.5
1.2-1.6
WLS for SPring-8 (Japan)
2000
10.3 (10.0)
40
1042
20
8
0.4-0.6
BAM WLS for (BESSY-II, Gernany)
2000
7.5 (7.0)
52
972
32
1.9
0.4-0.5
PSF-WLS (BESSY-II, Germany)
2001
7.5 (7.0)
52
972
32
1.9
0.4-0.5
Superbend (BESSY, Germany)
2004 9.6 (8.5)
46 177 32 1.9 0.5
List of Superconducting Wave Length Shifters at Budker INP
Superconducting Wave Length Shifters (WLS)Shifter represents 3-pole magnet with zero first and second field integrals along a trajectory. The central pole of the magnet has strong magnetic field and is used for generation of hard X-ray SR, while side poles are used for orbit correction.
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10 Tesla WLS on Spring-8
Beam orbit inside a standard (three-pole) wiggler has a bump so, that a point of radiation fromField maximum of of central pole is not on wiggler axis andDuring field change it moves in horizontal directionperpendicular to beam movement.
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7 Tesla WLS for BESSY-2
-2000 -1500 -1000 -500 0 500 1000 1500 2000-2
-1
0
1
2
3
4
5
6
7
Longitudinal magnetic field distribution along staight section for different field levels: 2.3, 4, 6, 7 Tesla
Ma
gn
etic
fie
ld, T
esl
a
Longitudinal distance, mm
General viewSC WLS
Correctors
e-
Top view
Side view
• Wave Length Shifter with fixed radiation point, where the superconducting part of magnet has non-zero first field integral and requirements of zero field integrals are performed by normally conducting correcting magnets which are outside of shifter cryostat.
• This variant of shifter allows to compensate for the first and second field integrals over each ½ shifter parts so that in the central pole the radiation point will be always on an straight section axis at any field level of the shifter.
-2000 -1500 -1000 -500 0 500 1000 1500 20000
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Orbit displacement in straight section at 1.9 GeVfor different field levels: 2.3, 4, 6, 7 Tesla
O
rbit
dis
pla
cem
en
t, m
m
Longitudinal distance, mm
Normal conductingCorrector-magnets
Superconducting magnets
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9 Tesla superbend prototype for BESSY-2 (2003)
All mentioned above devices are intended to be installed into straight sections of storage rings. For storage rings with energy up to 2 GeV the spectrum from bending magnet is limited to energy of photons up to 25 keV and it strongly limits possibilities of realization of experiments.
Superbend is a rather cheap approach allowing to considerably expand possibilities for experiments of already existing and expensive experimental stations, needing expanded spectrum in its hard end.
A disadvantage of the Superbend is that in comparison with a superconducting high-field insertion devices it is a basic element of the storage ring and all its systems should be not less reliable than conventional magnetic elements forming the storage ring.
Main parameters of SuperBend
Maximum Field (required /reached), T
9 .0 / 9.6
Magnetic gap, mm 46 Beam vacuum chamber: Vertical, mm Horizontal, mm
30 75
Current in superconducting coils, A 300 Storage energy, kJ 220 Cold mass, kg ~1300 Liquid helium consumption, l/h <1 Ramping time to 9 T ~15 min Bending angle, degree 11.25 Bending radius, m 0.905 m Edge angle, degree 1.3 Effective magnetic length, m 0.1777 Distance from flange to flange, m 0.55
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External housing
20K shield
60K shieldIron yoke
coils
Room temperature vacuum chamberBeam orbit
Liquid helium vessel
Superbend cross -section in median plan
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Following the idea to change normal conducting magnet by superbends, Budker INP in collaboration with BESSY-2 designed, fabricated and tested in 2003 a prototype superconducting bending magnet with the magnetic field above 9 Tesla using combined Nb-Ti and Nb-Sn superconducting wire.
Cold part of Superbend for BESSY-2
Assembled BESSY-2 Superbend.(Quench at 9.6 Tesla)
Normal conducting bending magnets
Superconducting bending magnets
(superbends)
Proposal of compact SR source with energy E=1.2 GeV, Bsc=8.5 Tesla
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13 Tesla supercoducting solenoids for VEPP-2000
General view of VEPP-2000 collider
13T SC solenoids
Measured magnetic field distribution along the solenoid axis.
Scheme of coils distribution in superconducting solenoid
Assembled solenoid
0 100 200 300 400 500 600 700 800 900-10
-8
-6
-4
-2
0
2
4
6
8
10
12
14
0 100 200 300 400 500 600 700 800 900
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
14
Ma
gn
etic fie
ld, T
esla
Longitudinal coordinate, mm
K
Cryostat of the solenoid in axial
section.
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List of superconducting wigglers of Budker INP
Year
Magnetic field, T
Max/ normal
Number of poles (Main +
side)
Magnetic gap,
mm
Period, mm
Vertical aperture,
mm
Liquid helium
consumption, LHe liter/hour
Multipole wiggler for VEPP-3
1979
(3.6) 3.5
20 15
90
8
4
VEPP-2 (Budker INP, Russia)
1984
(8.5) 8
5
26.5
240
15
4
Multipole wiggler for (BESSY-II, Germany)
2002
(7.67) 7
13+4
19
148 13
0.4-0.6
Multipole wiggler for ELETTRA (Italy)
2002
(3.7) 3.5
45+4
16.5
64
11
0.4-0.6
Multipole wiggler for CLS (Canada)
2005
(2.2) 2
61+2
13.5
34
9.5
0.-0.05
Multipole wiggler for DIAMOND (England)
2006
(3.75) 3.5
45+4
16.5
60
11.
0.-0.05
Multipole wiggler for SIBERIA-2 (Russia)
To be
2006
(7.7 prototype
) 7.5
19+2
19 164 14 0.-0.05
Multipole wiggler -2 for CLS
To be
2007
(4.34 prototy
pe) 4.0
25+2 14.5 48 10 0-05
Superconducting Wigglers (SCW)
Superconducting вигглеры represent sign-variable magneticChain манитов with equal to zero in the first and second integral of a field. InsideSuch system movement of a bunch occurs on a trajectory close to Sine wave, with small enough fluctuation of a horizontal corner,That leads to concentration of all radiation inside of this corner.
-Bo -Bo
Bo
-Bo
Bo
-Bo-Bo -Bo
-Bo
Bo
-Bo
C)
-Bo
B)
Bo Bo
Bo/2
A)
Bo Bo
Bo
Bo/2
3/4Bo
-1/4Bo
3/4Bo
-1/4Bo
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Optimization of wiggler parametersOptimization of wiggler period includes:
•Maximal photon flux in defined spectral region, •Maximal length of straight section •Maximal radiated power from wiggler (photon absorber limitation)•Minimal vertical beam aperture •Superconducting wire properties 10 20 30 40 50 60 70 80 90 100
0
10
20
30
40
Wiggler period, mm
Pho
ton
flux
, a.u
.
.
Photon flux with energy range 1-4 keV versus wiggler period for CAMD LSU (magnet length – 2m,vertical aperture 15 mm, electron energy- 1.3 GeV)
1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0
, mm
0.0001
0.001
0.01
0.1
1
10
100
Inte
gra
ted
ph
oto
n f
lux
, a.u
.
= 31 mm
Flux
.
2-D map of photon flux (a.u.) in axis: x- period length, y- photon energy (Electron energy -3 GeV, magnet length 2 m,Vertical beam aperture – 8 mm, maximum radiated power 20 kWatt forBeam current 0.4 A (CELLS project)
Photon flux with energy range 10-40 keV versus wiggler period for CELLS (magnet length – 2m,vertical aperture 8 mm, electron energy- 3 GeV)
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Superconducting coils of Superconducting coils of ELETTRA wigglerELETTRA wiggler
SC Wire characteristics
Diameter, mm 0.87 (0.92)
Ratio of NbTi : Cu 0.43
Critical current, Amp 380 (at 7 T)
Number of filaments 8600
Sketch of ½ pole of magnet
Photo of ½ pole of the magnet
Two halves of magnet before assemblingTwo halves of magnet before assembling
0 10 20 30 40 502,6
2,8
3,0
3,2
3,4
3,6
3,8
Quench history ofELETTRA MPW prototype
Quench number
Mag
netic
fiel
d
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SPECTRAL CHARACTERISTICS OF the WIGGLER RADIATION • Multipole wigglers represent sign-alternating magnetic structure with many
poles with high magnetic field. Electron beam passing through multipole wiggler concentrates SR from all poles into the same horizontal angle and increase photon flux.
• In an ideal case for infinitely long periodic wiggler and for zero energy spread in electron beam the spectrum of radiation is line spectrum with energy maximum values defined by expression:
•
•• where n is the harmonic number, is the relativistic factor, 0 is the
undulator period, B0 is the magnetic field amplitude in median plane, is the undulator parameter defined below:
•
• The maximum of radiation from wiggler falls corresponds to harmonic number:
•
• For CLS wiggler the above parameters are: K~6.3, Nmax 95 and photon energy of the basic harmonic is equal 0.11 keV. In real situation, the spectrum of radiation is continuous due to final number of the wiggler periods, existence of energy and angular spread in electron beam.
)2/1(
22
0
2
K
nn
][][934.0 0 TeslaBcmK
3max 8/3 KN
1 2 3 4 5 6 7 8 9 101E14
1E15
1E16
Pho
ton
flux/m
rad/
0.1%
BW
Photon energy, keV
2 Tesla+ period disorder 1.86 Tesla +period disorder1.86 Tesla
E=2.9 GeVI=0.5A
Presented wiggler has rather complicated spectral structure with transition from spectra of undulator radiation to spectra of set of sign alternating bending magnets (wiggler) depending on energy of photons. XAFS experiments require smoothness of spectrum in range 5-40 keV. Effects of electron beam energy spread and final number of wiggler poles are not enough for spectrum smoothness in photon energy area 5-10 keV. To provide of required spectrum smoothness in low energy range it was required to bring in casual disorder in period length of the wiggler.
Superconducting 63 pole 2 Tesla wiggler for CLS (2005)
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CLS WIGGLER MAGNETIC SYSTEM
• The strong magnetic field on the wiggler axis median plane is created by 122 central and 4 side coils wound over the ARMCO-iron cores.
• The shape of the central pole is racetrack type with dimensions of 88 mm x16.6 mm2 and height of 23.85 mm.
• All coils consist of one section with total turns number of 105.
• Central coils (122 ps) are energized by two independent power supplies with maximum current 400 A each where currents are summarized.
• The Additional 4 side coils are energized by 1 power supply giving a possibility to adjust first field integral to zero. .
Wire diameter with/without insulation, mm 0.91/0.85
Ratio of NbTi : Cu 1.4
Number of filaments 312
Critical current at 7 Tesla(Amp) 510-550
Number of filaments in wire 312
Wire and coils parameters
Photos of the magnet coils.
Sketch of the magnet coils.
Critical magnetic field value vs the SC wire current
at the temperature 4.2 K
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Main polesmagnetic fieldnumber of poles¾ polesmagnetic fieldnumber of poles¼ polesmagnetic fieldnumber of poles
3.5 T45
2.8 T2
1.0 T2
Pole gap 16 mm
Period length 60 mm
Coils material NbTi wire
Current in coil for 3.5 Tesla ~620A
Stored energy for 3.6 Tesla ~40kJ
Main parameters of superconducting Main parameters of superconducting wiggler for DLSwiggler for DLS
½ pole of the wiggler
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8B, Tesla
0
40
80
120
160
200
240
280
320
360
I, A
Iside
Imain
The currents Iside and Imain for zero first field integral versus magnetic field
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Magnetic f
ield
,Tesla
Longitudinal coordinate, m
Longitudinal SC wiggler magnetic field distribution at 3.5 Tesla
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1 11 21 312 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 22 23 24 25 26 27 28 29 30 32
Quench number
3
3.2
3.4
3.6
3.8
Mag
net
ic f
ield
, Tes
la
Quench history
SAT
FAT
Bath cryostat test
Quench history of superconducting Quench history of superconducting wiggler for DLSwiggler for DLS
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
-0.010
-0.008
-0.006
-0.004
-0.002
0.000
0.002
Magnetic f
iel, T
esla
Longitudinal coordinate, m
Remanent magnetic field after setting zero currents in the coils
200 400 600 800 1000 1200 1400 1600-0.0010
-0.0005
0.0000
0.0005
0.0010
0.0015
B T
X mm
BT
Remanent magnetic field after quench
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WIGGLER CRYOGENIC SYSTEM
Used equipment:
•Cooling of shield screens is made by means of 2 stage cryocoolers (Leybold, Sumitomo) with temperatures 20К and 60К•2 stage cryocoolers with temperatures 4K and 50K (recondensors) are used for heat inleak reduction into liquid helium and recondensation of the evaporated helium (Leybold, Sumitomo) •HTSC current leads are used to reduce heat inleak into liquid helium
20K Copper liner is used In superconducting multipole wigglers to remove all heat created by electron beam
Some cryostat concepts in which cryocoolers for refrigerating of evaporated He were used for WLS and wigglers. Cryocooler heat exchangers were placed inside liquid helium vessel. The cooler performance is low in such cheme low liquid helium consumption was about 0.5 liter per hour.
More effective cryostat concept is a cryostat where cryocoolers are used for interception of heat inleak into liquid helium vessel. This concept of cryostat gives zero liquid helium consumption for normal cryocooler operation.Cryocooler efficiency of work degrades with time and liquid helium consumption became not zero. Average liquid helium consumption during an year is estimated as 0.05 litres per hour under condition of annual technical service of the coolers.
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WIGGLER CRYOGENIC SYSTEM
49 pole SC wiggler For Diamond Light Source under SiteAcceptance Test
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WIGGLER CRYOGENIC SYSTEM
• Current leads feeding the magnet with current 400А are the main source of heat in-leak into liquid helium vessel due to both heat conductivity and joule heat. Each current lead consists of two parts: normal conducting brass cylinder and high-temperature superconducting ceramics.
• One pair of current leads assembled into one block together with 2 stage cooler 4.2GM which is placed in insulating vacuum of the cryostat.
• The junctions of normally conducting and superconducting parts of current leads are supported at temperature 50-65K by first stage of coolers.
• The lower part of a superconducting part of the current lead is connected with superconducting Nb-Ti cable and supported at temperature below 4.2K with the help of the second stage of the coolers.
• Power of 2-nd stage of the coolers is approximately twice more than heat in-leak power at lower end of superconducting current leads and the rest cooler power is used for cooling liquid helium vessel.
Current lead block
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30Tim e, h
0
20
40
60
80
Te
mp
era
ture
, K
January 19-20, 2005Magnet (bottom)
Magnet (top)
LHe tank
+Ic
+Is
Screen 20K
Screen 60K
Rec. 4K (in)
Rec. 4K (out)
B, Tesla
0
0.5
1
1.5
2
2.5
B, T
es
la
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Main temperature probes values versus time at different field level of the wiggler.
Brass current lead
HTSC current lead
Coolpower 4.2GM
60K stage
4K stage
Vacuum-LHe feedthrough
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Vacuum chamber and copper liner
Liquid helium vessel with vacuum chamberfittings
Beam vacuum chamber system
Copper liner
LHe vessel
Insulating vacuum is separated from UH vacuum of a storage ring and keep at vacuum level 10-6 – 10-7Torr by 300l/s ion pump
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Wiggler Control system
Digitalinput/output
MVME172
SM1
Analoginput
TIP866-10(RS232, 8 channels)
Digitalinput/output
VME crate
COOLPACK 6200 MD
compressor units
(to COOLPOWER 4.2GM)
(to COOLPOWER 4.2GM)
(to COOLPOWER 10MD)
(to COOLPOWER 10MD)
Cryogenic system monitoring
Interlock signals
Quench detector
DANFYSIK MPS 883
(400A/10V)
SCW (magnet&cryostat)
PS1 (main)
PS2 (auxiliary)
Junction box
1
2
3
4
SCW control consoleC
LS
Lo
cal A
rea
Net
wo
rk
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Thank you