Transcript Document 7449046

Superconducting magnets
for SR generation in Budker
INP: the status of works
N.A. Mezentsev
Budker INP, Novosibirsk, Russia
RUPAC-2006, Novosibirsk
1
INTRODUCTION
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).
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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.
List of Superconducting Wave Length Shifters at Budker INP
Year
Magnetic Magnetic Magnetic Vertical
field, T gap, mm length, aperture,
Max/
mm
mm
normal
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- 1998
CAMD (USA)
7.55
(7.0)
51
972
32
1.5
1.2-1.6
WLS for SPring-8 2000
(Japan)
10.3
(10.0)
40
1042
20
8
0.4-0.6
BAM WLS for
(BESSY-II,
Gernany)
PSF-WLS
(BESSY-II,
Germany)
Superbend
(BESSY,
Germany)
2000
7.5
(7.0)
52
972
32
1.9
0.4-0.5
2001
7.5
(7.0)
52
972
32
1.9
0.4-0.5
2004
9.6
(8.5)
46
177
32
1.9
0.5
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Beam orbit inside a standard (three-pole)
wiggler has a bump so, that a point of radiation from
Field maximum of of central pole is not on wiggler axis and
During field change it moves in horizontal direction
perpendicular to beam movement.
10 Tesla WLS on Spring-8
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7 Tesla WLS for BESSY-2
SC WLS
Side view
e-
Superconducting
magnets
Normal conducting
Corrector-magnets
Longitudinal magnetic field distribution along staight section
for different field levels: 2.3, 4, 6, 7 Tesla
7
6
Correctors
Magnetic field, Tesla
5
4
Top view
3
2
1
•
0
-1
-2
-2000
-1500
-1000
-500
0
500
1000
1500
2000
Longitudinal distance, mm
Orbit displacement in straight section at 1.9 GeV
for different field levels: 2.3, 4, 6, 7 Tesla
16
15
14
13
Orbit displacement, mm
12
11
10
9
•
8
7
6
5
4
3
2
1
0
-2000
-1500
-1000
-500
0
500
1000
Longitudinal distance, mm
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1500
2000
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.
5
9 Tesla superbend prototype for BESSY-2 (2003)
Main parameters of SuperBend
Maximum Field
(required /reached), T
Magnetic gap, mm
Beam vacuum chamber:
Vertical, mm
Horizontal, mm
Current in superconducting coils, A
Storage energy, kJ
Cold mass, kg
Liquid helium consumption, l/h
Ramping time to 9 T
Bending angle, degree
Bending radius, m
Edge angle, degree
Effective magnetic length, m
Distance from flange to flange, m
9 .0 / 9.6
46
30
75
300
220
~1300
<1
~15 min
11.25
0.905 m
1.3
0.1777
0.55
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.
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Superbend cross -section in median plan
External housing
20K shield
60K shield
Beam orbit
Room temperature vacuum chamber
Iron yoke
coils
Liquid helium vessel
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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
Normal conducting
bending magnets
Assembled BESSY-2 Superbend.
(Quench at 9.6 Tesla)
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
13T SC solenoids
General view of VEPP-2000 collider
Scheme of coils distribution in superconducting solenoid
Magnetic field, Tesla
0
100
200
300
400
500
600
700
800
K 900
14
14
12
12
10
10
8
8
6
6
4
4
2
2
0
0
-2
-2
-4
-4
-6
-6
-8
-8
-10
0
100
200
300
400
500
600
700
800
-10
900
Longitudinal coordinate, mm
Assembled solenoid
Cryostat of the solenoid in axial
section.
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Measured magnetic field
distribution along the
solenoid axis.
9
Superconducting Wigglers (SCW)
Superconducting вигглеры represent sign-variable magnetic
Chain манитов with equal to zero in the first and second integral
of a field. Inside
Such 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.
A)
Bo
Bo/2
Bo
-Bo
-Bo
Bo/2
-Bo
B)
Bo
List of superconducting wigglers of Budker INP
Bo
Bo
-Bo
Bo
-Bo
-Bo
C)
Multipole wiggler for
VEPP-3
1979
(3.6)
3.5
20
15
90
8
Liquid
helium
consump
tion, LHe
liter/hour
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
(3.75)
3.5
45+4
16.5
60
11.
0.-0.05
(7.7
19+2
19
164
14
0.-0.05
25+2
14.5
48
10
0-05
Year
Multipole wiggler for
DIAMOND (England)
2006
Multipole wiggler for
SIBERIA-2 (Russia)
To
be
2006
-2
To
be
2007
Multipole wiggler
for CLS
Magneti
c field, T
Max/
normal
Number
of poles
(Main +
side)
Magneti
c gap,
mm
Period,
mm
Vertical
aperture,
mm
Bo
3/4Bo
-1/4Bo
-Bo
Bo
-Bo
3/4Bo
-Bo
-1/4Bo
prototype
)
7.5
(4.34
prototy
pe)
4.0
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Optimization of wiggler parameters
40
Optimization of wiggler period includes:
Photon flux, a.u.
30
•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
20
10
0
10
20
30
40
50
60
70
80
90
100
.
Wiggler period, mm
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)
100
Integrated photon flux, a.u.
10
.
1
0.1
= 31 mm
0.01
0.001
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 for
Beam current 0.4 A (CELLS project)
0.0001
10
15
20
25
30
35
, mm
40
45
50
55
60
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
ELETTRA wiggler
Quench history of
ELETTRA MPW prototype
3,8
Sketch of ½ pole of magnet
3,6
3,4
Magnetic field
Photo of ½ pole of the magnet
3,2
3,0
2,8
2,6
0
10
20
30
40
50
Quench number
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
Two halves of magnet before assembling
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Superconducting 63 pole 2 Tesla wiggler for CLS (2005)
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:
•
n 
•
•
2 2n
0 (1  K 2 / 2)
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:
•
K  0.934  0[cm]B[Tesla ]
•
•
•
The maximum of radiation from wiggler falls corresponds to harmonic
number:
N max  3 / 8K 3
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.
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.
1E16
Photon flux/mrad/0.1%BW
•
2 Tesla+ period disorder
1.86 Tesla +period disorder
1.86 Tesla
1E15
E=2.9 GeV
I=0.5A
1E14
1
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3
4
5
6
7 8 9 10
Photon energy, keV
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CLS WIGGLER MAGNETIC SYSTEM
Wire and coils parameters
•
•
•
•
•
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. .
Sketch of the magnet coils.
Photos of the magnet coils.
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
Critical magnetic field value vs the SC wire current
at the temperature 4.2 K
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Main parameters of superconducting
wiggler for DLS
Main poles
magnetic field
number of poles
¾ poles
magnetic field
number of poles
¼ poles
magnetic field
number of poles
3.5 T
45
2.8 T
2
1.0 T
2
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
½ pole of the wiggler
3.5
3.0
2.5
360
Iside
Imain
2.0
320
Magnetic field,Tesla
1.5
280
240
200
1.0
0.5
0.0
-0.5
I, A
-1.0
-1.5
160
-2.0
-2.5
120
-3.0
80
-3.5
0.2
40
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Longitudinal coordinate, m
0
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
B, Tesla
2.8
3
3.2
3.4
3.6
3.8
Longitudinal SC wiggler magnetic field distribution at 3.5 Tesla
The currents Iside and Imain for zero first field integral versus magnetic field
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Quench history of superconducting
wiggler for DLS
0.002
Quench history
3.8
Magnetic fiel, Tesla
0.000
3.6
-0.002
-0.004
FAT
-0.008
3.4
-0.010
SAT
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Longitudinal coordinate, m
Bath cryostat test
Remanent magnetic field after setting zero currents in the coils
0.0015
3.2
BT
0.0010
3
0.0005
1
2 3 4 5 6 7 8 9 10
11
12 13 14 15 16 17 18 19 20
21
22 23 24 25 26 27 28 29 30
31
32
BT
Magnetic field, Tesla
-0.006
Quench number
0.0000
-0.0005
-0.0010
200
400
600
800
X mm
1000
1200
1400
1600
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 Site
Acceptance Test
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2.5
January 19-20, 2005
B, Tesla
2
WIGGLER CRYOGENIC SYSTEM
1
0.5
Current lead block
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
0
2
4
6
8
10
12
14
16
Time, h
18
20
22
24
26
28
30
80
Main temperature
probes values
versus time at
different field level
of the wiggler.
60
Temperature, K
• 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.
Magnet (bottom)
Magnet (top)
LHe tank
+Ic
+Is
Screen 20K
Screen 60K
Rec. 4K (in)
Rec. 4K (out)
B, Tesla
1.5
40
20
0
Coolpower 4.2GM
Brass current lead
60K stage
HTSC current lead
4K stage
Vacuum-LHe feedthrough
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Vacuum chamber and copper liner
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
Liquid helium vessel with vacuum chamber
fittings
Beam vacuum chamber system
Copper liner
LHe vessel
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Wiggler Control system
VME crate
MVME172
SCW control console
TIP866-10
(RS232, 8 channels)
SM1
CLS Local Area Network
Digital
Digital
input/output
input/output
Junction box
Analog
input
Interlock signals
Quench detector
Cryogenic system
monitoring
COOLPACK
6200 MD
compressor units
1
DANFYSIK
MPS 883
(400A/10V)
(to COOLPOWER 10MD)
2
(to COOLPOWER 10MD)
PS1 (main)
3
(to COOLPOWER 4.2GM)
4
PS2 (auxiliary)
(to COOLPOWER 4.2GM)
SCW (magnet&cryostat)
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Thank you
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