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


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


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.


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.


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


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


External housing

20K shield

60K shieldIron yoke

coils

Room temperature vacuum chamberBeam orbit

Liquid helium vessel

Superbend cross -section in median plan


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


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.


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


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)


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


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)


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


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


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


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.



49 pole SC wiggler For Diamond Light Source under SiteAcceptance Test



• 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


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


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


Thank you

superconducting magnets for sr generation in budker inp: the status of works

Documents

field integrals

novosibirskyearmagnetic

field level

pole magnets shifters

magnetic field b

strong magnetic field

pole wiggler

central pole