Wiggler Optimization for Emittance Control: Experience at CESR-c

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1 Wiggler Optimization for Emittance Control: Experience at CESR-c A. Temnykh for CESR operating group LEPP, Cornell University, Ithaca, NY 18, USA D. Rice D. Rubin J. Crittenden S. Chapman J. Codner R. Gallagher Y. He J. Kandaswamy V. Medjidzade A. Mikhailichenko N. Mistry T. Moore E. Nordberg S. Richichi E. Smith K Smolenski W. Trask

2 CESR-c Wiggler main characteristics.1t peak field, cm period, cm pole width, 7.6cm gap, 9xcm beam clearance 8 poles (asymmetric magnetic design) Iron poles & superconductive coils (superferric technology) Cryogenic performance: ~1.3W at K and ~W at 77K Wigglers used to: Enhance radiation damping control beam emittance wiggler cluster in ring A. Temnykh WIGGLE Workshop, Frascati

3 Contents Why we need wiggler magnets Setting the main parameters: peak field, length, period, technology, magnetic design Production, magnetic field measurement, quality control and cost. Wigglers characterization with beam and model benchmarking. Conclusion A. Temnykh WIGGLE Workshop, Frascati 3

4 Why we need wigglers In 1 the decision was made to modify CESR to provide luminosity over the energy range from 1. to. GeV/beam. Without wigglers, luminosity L ~ E (:7) (empirical law) will be decreased by factor of 6 to 1. Not acceptable, need wigglers! With wigglers, beam energy spread σ e /E ~ Bw 1/, damping rate 1/τ B wlw, horizontal beam emittance ε x ~ BwHw Luminosity ~ 3x1 3 [1/sec/cm], reduction factor ~ A. Temnykh WIGGLE Workshop, Frascati

5 Setting the main parameters: peak field and total length Peak field (Bw) is limited by maximum allowed energy spread: σ e /E ~ 8e- => Bw ~.1T Active length (Lw) should be enough to recover damping rate: 1/τ ~ 3 sec -1 => Lw ~ 18m Period: Longer period results in weaker cubic non-linearity, but increases orbit excursion which increase sensitivity to field non-uniformity across wiggler poles. Reasonable compromise: l = cm BL w π 3 y' = y+ y +... ( Bρ) 3 λ.3. Vertical field variation across cm pole. From 3D model calculation Bmax = 1.7T Bmax =.1T Lxp By( x) Bw λ x' = ; xp = ( Bρ) x Bρ π Expected field non-uniformity for cm pole width and 7 cm gap A. Temnykh WIGGLE Workshop, Frascati x[mm]

6 Setting the main parameters: technology Modular design, ~ 1.m per unit, with cm x 9cm beam clearance. Normal conducting copper/iron. Similar sized magnets required ~3kW/wiggler. Permanent magnet (NdFeB). T in cm x 9cm gap difficult, BIG magnets, $$, must be opened or removed for GeV running. Superferric technology (iron poles & superconducting coils) only viable option for high (T) fields over given beam aperture. From D.Rice presentation: CESR-c Wiggler Manufacture - PAC 3 A. Temnykh WIGGLE Workshop, Frascati 6

7 Setting the main parameters: type of symmetry Poles length [cm] Bmax/pole [T] 7 poles (symmetric) = /.1/-.1/.1/-.1/.1/ poles (asymmetric) = /.1/-.1/.1/-.1/.1/-.1/1.1 Field along magnet Beam trajectory A. Temnykh WIGGLE Workshop, Frascati 7

8 Setting the main parameters: type of symmetry Symmetric design (7 poles) Cubic non-linearity (vertical) % smaller for fixed damping Only types of poles (vs. 3) Asymmetric design (8 poles) Horizontal orbit excursion two times smaller Integrated magnetic field quality is not sensitive to systematic errors on in poles. Maintains linearity over wider range of excitation levels Units 1 & are 7-pole, units 3 and up are 8-pole. We built 16 units total A. Temnykh WIGGLE Workshop, Frascati 8

9 Production: cold mass general view (7-pole version) 13cm 7cm thick yoke plate flux return and support. 7.6cm Iron poles with superconductig coils cm A. Temnykh WIGGLE Workshop, Frascati 9

10 Production: Coil Winding Coils are wound directly on individual machined iron poles. Main poles 66 turns,.7 mm, 7 filament wire Wet wound with Epotek T9 epoxy Clamped with shim blocks every layers to maintain mechanical tolerances. Experienced winder produces 1/day Beam axis From D.Rice presentation: CESR-c Wiggler Manufacture - PAC 3 A. Temnykh WIGGLE Workshop, Frascati 1

11 Production: Coil Winding From D.Rice presentation: CESR-c Wiggler Manufacture - PAC 3 A. Temnykh WIGGLE Workshop, Frascati 11

12 Production: Assembly with preload The finished pole pieces are placed on a 7 mm thick yoke plate flux return and support. Magnetic force & cooldown shrinkage require large preload on coils 16 Ton MPa pressure From D.Rice presentation: CESR-c Wiggler Manufacture - PAC 3 A. Temnykh WIGGLE Workshop, Frascati 1

13 Magnetic field measurement: field mapping with Hall probe Wiggler#1, 7poles By(z), Hall probe measurement and model calculation Difference between measurement and calculation A. Temnykh WIGGLE Workshop, Frascati 13

14 Magnetic field measurement: field integrals measurement with stretched coil First integral with straight coil: Flux 1 l ~ st I1 = = abzdz ( ) = Bzdz ( ) = I1 a a Second integral with twisted coil: l Flux 1 l 1 l z l l ~ tw I = = Bzazdz ( ) ( ) = Bza ( ) (1 ) dz = Bzdz ( ) Bzzdz ( ) = I1 I a a a l l l A. Temnykh WIGGLE Workshop, Frascati 1

15 Magnetic field measurement: wiggler #1(7pole) stretched coil measurement Variation of I1y versus x, Wiggler #1 ( 7pole ) magnetic measurement with long flipping coil. July 6, ST 6 #1 (7-pole) norm 1 Variation of I1x versus x, Wiggler #1 ( 7pole ) magnetic measurement with long fliping coil. July 6, ST #1 skew - Im = 11A, Bmax ~ 1.7 T 1A 13A - 17A 16A, Bmax ~.1T Im=11, B ~ 1.7T - 1A 13A 17A 16A, B ~.1 T A. Temnykh WIGGLE Workshop, Frascati 1

16 Magnetic field measurement: wiggler #(8pole) stretched coil measurement Variation of I1y versus x ( Normal field integral, b subtracted) Wiggler # (8 Poles) magnetic measurement with a long flipping coil. Feb 19 3, ST 6 1 Variation of I1x with x, ( Skew field integral) Wiggler # (8Poles) magnetic measurement with long fliping coil. Feb 19 3, ST - - I = 99A (1.7T) 19A 1A 13A (.1T) - I = 99A (1.7T) 19A 1A 13A (.1T) A. Temnykh WIGGLE Workshop, Frascati 16

17 Production: pole quality control Warm magnetic field measurement setup for pole testing, Imax~ 1A. Compare tested pole field profile with reference. Check for missing turns Turn-to-turn shorting Pickup coil Tested pole Sliding stage "z" scan ( along beam axis) A. Temnykh WIGGLE Workshop, Frascati 17

18 Production: quality control shorts, missing turns checking Warm magnetic measurement: "z" scan ( along beam axis) Tested pole field profile Difference from reference pole ( x 66) Bpole db x Bpole db x Bpole db x Repeatability -. Good pole -.6 Bad pole, layers (turns) shorted -1 A. Temnykh WIGGLE Workshop, Frascati 18

3. Skew quadrupole component in CESRc wigglers Production period Jul - Mar 3 7-pole Production: quality control a1 - problem Production period Jul 3 - Mar Explanation:

19 3. Skew quadrupole component in CESRc wigglers Production period Jul - Mar 3 7-pole Production: quality control a1 - problem Production period Jul 3 - Mar Explanation: variation in coil geometry Upper pole x 1. Lower pole B x x 1 Pole sorting Unit # Unit # Poles rearranged A. Temnykh WIGGLE Workshop, Frascati 19

Production: quality control a1 - problem Warm magnetic measurement: "x" scan.1 Bpole db x 66. -9-39 -9-19 -9 Pole ends -. -.1 -.1 -. -. "x" scan ( across beam axis) Two peaks at the pole ends indicated that tested pole -.

20 Production: quality control a1 - problem Warm magnetic measurement: "x" scan.1 Bpole db x Pole ends "x" scan ( across beam axis) Two peaks at the pole ends indicated that tested pole -.mm narrower than "reference". A. Temnykh WIGGLE Workshop, Frascati

21 Wiggler a1 component effect on coupling One wiggler (Oct ) and 1 wiggler (Jan ) optics Wiggler location Nov, One wiggler (#1) optics. Wave analysis indicated coupling source ( ~ Gm/cm) at wiggler location, ~1.Gm/cm from magnetic measurement. Wave fitting Jan, 1 wigglers optics. Wave analysis indicated no coupling source at wigglers location. Wave fitting A. Temnykh WIGGLE Workshop, Frascati 1

22 Production: resources and cost When in full production, committed resources are: Sr. Technical & Supervisory:. FTE Technical support: 13 FTE Approximate cost per wiggler unit for parts and outside machining and manufacturing below $1k Results in production of one wiggler every ~3 weeks A. Temnykh WIGGLE Workshop, Frascati

23 Wiggler characterization with beam and model benchmarking. Model Based on BMAD subroutine library (homemade): (D. Sagan) Wiggler model used calculated 3D field map. Details are in "ICFA Beam Dyn.Newslett.31:8-,3" by D.Sagan, et. al. Comparison between measurement and prediction (model benchmarking). Bunch length and beam energy spread Tune variation with wiggler field Tune variation with beam position in wiggler Tune variation with amplitude (octupole moment) A. Temnykh WIGGLE Workshop, Frascati 3

Wiggler characterization with beam and model benchmarking. 7 6 3 1 CESRc bunch length measurement Optics: HIBETAINJ_68. Dec 11, fs = 39., st sig_z = 11.86 +-.

24 Wiggler characterization with beam and model benchmarking CESRc bunch length measurement Optics: HIBETAINJ_68. Dec 11, fs = 39., st sig_z = mm Bunch length and beam energy spread z[mm] Streak camera measurement σ E E π = α A. Temnykh WIGGLE Workshop, Frascati f s c σz α=.11, σz σ = E fs ; 39 khz, = 11.86mm σ E Model prediction: E = (7% from wigglers)

25 .3..1 Wiggler characterization with beam and model benchmarking. Wiggler transfer functions, x'(x) and y'(y) and local focusing effect. Horizontal transfer function ( x' vs x) and local focusing effect ( dx'/dx) calculated with tracking trough 3D wiggler magnetic field x'[mrad] Horizontal plane Tune variation with beam position, model Vertical transfer function ( y' vs y) and local focusing ( -dy'/dy) calculated with tracking trough 3D wiggler magnetic field - dy'/dy [1/m] Vertical plane dx'/dx [1/m] y'[mrad] x[mm] A. Temnykh WIGGLE Workshop, Frascati y[mm].9.8

26 Wigglers characterization with beam and model benchmarking Vetical tune variation with wiggler 1WA current, measurement and calculation CESRc MS, Feb 1.1 Tune variation with wiggler (1WA) current Imain[A] / 1WA dqv - measured model dqh - measured model Q 1 β 1 π f 1 dy' BI () = f dy B Value Error dqh/di (model) -.97e- 6.7e-13 dqh/di (measl) 3.e-.9e- dqv/di (model).1.e-11 dqv/di (meas) e- A. Temnykh WIGGLE Workshop, Frascati 6

27 Wiggler characterization with beam and model benchmarking Tune variation with beam position in 18E cluster (3wigglers). Vertical and horizontal tune versus vertila beam position at three 8-pole wigglers cluster, VB 8. (ST, Aug 1 3) dfh[khz] - measured dfv[khz] - measured dfh[khz] / model dfv[khz] / model Vertical and horizontal tunes measured as a function of vertical orbit position in wigglers df = 1kHz dq =. hv, hv, +- 1mm A. Temnykh WIGGLE Workshop, Frascati VB8 bump, 1 cu ~ 1mm vert orbit shift

28 Wiggler characterization with beam and model benchmarking Tune variation with beam position in 18E cluster (3wigglers). Vertical and horizontal tunes measured as a function of horizontal orbit position in wigglers df = 1kHz dq =. hv, hv, Vertical and horizontal tune versus horizontal beam position at three 8-pole wigglers cluster, HB 7. (ST, Aug 1 3) dfh[khz] - measured dfv[khz] - measured dfh[khz] / model dfv[khz] / model HB7 bump, 1cu ~ 1mm horizontal orbit displacment A. Temnykh WIGGLE Workshop, Frascati 8

29 Wiggler characterization with beam and model benchmarking Tune variation with beam position in 18W cluster (3wigglers). Vertical and horizontal tunes measured as a function of horizontal orbit position in wigglers df = 1kHz dq =. hv, hv, Vertical and horizontal tune versus horizontal beam position at three wigglers cluster, wig1_18w, wig_18w, wig3_18w (July 8 ) 6 - dfh[khz] measured dfv[khz] measured dfh[khz] model dfv[khz] model HBS, 1cu ~ 1mm horizontal orbit displacment A. Temnykh WIGGLE Workshop, Frascati 9

30 Wiggler characterization with beam and model benchmarking Setup for measurement of tune variation with amplitude. Tune tracker (tune) Phase shifter + Amplifier BPM (amplitude) 1 Turn - by - turn beam position Vertical shaking, BMP W Shaker Receiver - Tune tracker provides beam resonance shaking with stable amplitude horizontal/vertical plane. -1 turn # y = Ay*cos((m-m)*36*Qy) Value Error Ay[mm] m Qy.616. A. Temnykh WIGGLE Workshop, Frascati 3

31 Wiggler characterization with beam and model benchmarking. Measured and calculated dependence of vertical/horizontal tune versus vertical/horizontal amplitude Vertical tune as function of vertical amplitude..1 Measurement Model Model with wigglers OFF Horizontal tune as function of horizontal amplitude..1 Measurement Model Model with wigglers OFF.1.1 dqh = m * Av[mm]^ meas.8937e- model.1e- model wigglers OFF e-6. dqv = m * Av[mm]^ meas.3 model.3 model wigglers OFF -.8e Ay [mm] at beta_y = 1m Ax [mm] at beta_x = 1m A. Temnykh WIGGLE Workshop, Frascati 31

32 Conclusion We have built 16 superferric wigglers, 1 of them have been installed in the ring and now under operation. Beam based wiggler characterization is in good agreement with model. We have good wigglers and reliable model So far, we have not seen beam performance degrading due to wiggler field nonlinearities. Very positive experience. A. Temnykh WIGGLE Workshop, Frascati 3

33 6 - - Variation of I1y versus x, Wiggler # ( 7 Poles ) magnetic measurement with long flipping coil. Jan 1 3, ST Imain = (1.7T) 18A 1A 13A Imain = 1A (.1T) Magnetic measurement summary. Units 1 and are 7-pole, units 3 and up are 8-pole # (7-pole) norm Variation of I1y versus x ( Normal field integral, b subtracted) Wiggler # (8 Poles) magnetic measurement with a long flipping coil. Feb 19 3, ST 6 # norm Variation of first integral of horizontal field with x, Wiggler # ( 7 Poles ) magnetic measurement with long fliping coil. Jan 1 3, ST # skew Imain = ( 1.7T) 18A 1A 13A 1A (.1T) Variation of I1x with x, ( Skew field integral) Wiggler # (8Poles) magnetic measurement with long fliping coil. Feb 19 3, ST # skew Variation of I1y versus x, Wiggler #1 ( 7pole ) magnetic measurement with long flipping coil. July 6, ST #1 (7-pole) norm Im = 11A, Bmax ~ 1.7 T 1A 13A 17A 16A, Bmax ~.1T Variation of I1y versus x. Wiggler #3 (8 Poles) magnetic measurement with long flipping coil. Feb 3, ST 6 Imain = 99A (1.7T) 19A 1A 13A (.1T) Variation of I1x versus x, Wiggler #1 ( 7pole ) magnetic measurement with long fliping coil. July 6, ST - -1 #1 skew Im=11, B ~ 1.7T 1A 13A 17A 16A, B ~.1 T Variation of first integral of horizontal field with x, Wiggler #3 (8Poles) magnetic measurement with long fliping coil. Feb 3, ST 1 #3 (8-pole) norm #3 skew Variation of I1y versus x. Wiggler # (8 Poles) magnetic measurement with a long flipping coil. Feb 8 3, ST 6 1 # norm B[G*m] B[G*m] B[G*m] B[G*m] B[G*m] Imain = 99A (1.7T) 19A 1A 13A (.1T) Variation of I1x with x, ( Skew field integral) Wiggler # (8Poles) magnetic measurement with long fliping coil. Feb 8 3, ST # skew - - I = 99A (1.7T) I = 99A (1.7T) - 19A 19A - B[G*m] - 1A 1A B[G*m] 13A (.1T) (.1T) B[G*m] - A. Temnykh WIGGLE Workshop, Frascati B[G*m] A B[G*m]

34 Variation of I1y (normal field) versus x. Variation of I1x with x, ( Skew field integral) Wiggler #6 (8 Poles) magnetic measurement with a long flipping coil. Wiggler #6 (8Poles) magnetic measurement with long fliping coil. March 18 3, ST March 18 3, ST 6 1 Variation of I1y (normal field) versus x. Wiggler #7 (8 Poles) magnetic measurement with a long flipping coil. August 17 3, ST 6 1 Variation of I1x with x, ( Skew field integral) Wiggler #7 (8Poles) magnetic measurement with long fliping coil. August 17 3, ST 99A 19A 1A #6 norm 13A #6 skew #7 norm 18A 1A 13A #7 skew A 19A A 1A 1A - 13A - 13A Variation of I1y (normal field) versus x. Wiggler #8 (8 Poles) magnetic measurement with a long flipping coil. October , ST Variation of I1x with x, ( Skew field integral) Wiggler #8 (8Poles) magnetic measurement with long fliping coil. October 8 3, ST Variation of I1y (normal field) versus x. Wiggler #9 (8 Poles) magnetic measurement with a long flipping coil. Oct 8 3, ST Variation of I1x with x, ( Skew field integral) Wiggler #9 (8Poles) magnetic measurement with long fliping coil. Oct 8 3, ST - #8 norm 18A 1A 13A 8 #8 skew #9 skew 6 - #9 norm 18A 1A 13A -6-18A - 18A 1A 1A -8 13A 13A Variation of I1y (normal field) versus x. Variation of I1x with x, ( Skew field integral) Wiggler #1 (8 Poles) magnetic measurement with a long flipping coil. Wiggler #1 (8Poles) magnetic measurement with long fliping coil. November 11 3, ST November 11 3, ST Variation of I1y (normal field) versus x. Wiggler #11 (8 Poles) magnetic measurement with a long flipping coil. Feb 6, ST Variation of I1x with x, ( Skew field integral) Wiggler #11 (8Poles) magnetic measurement with long fliping coil. Feb 6, ST 1 - #1 norm 18A 1A 13A #1 skew #11 norm #11 skew A. Temnykh WIGGLE 1 3 Workshop, Frascati A 1A - 18A 13A - 18A 1A - 1A 13A 13A

35 Variation of I1y (normal field) versus x. Wiggler #1 (8 Poles) magnetic measurement with a long flipping coil. Dec 3, ST #1 norm Variation of I1y (normal field) versus x. Wiggler #1 (8 Poles) magnetic measurement with a long flipping coil. Feb 16, ST #1 norm 18A 1A 13A 18A 1A 13A Variation of I1x with x, ( Skew field integral) Wiggler #1 (8Poles) magnetic measurement with long fliping coil. Dec 3, ST #1 skew Variation of I1x with x, ( Skew field integral) Wiggler #1 (8Poles) magnetic measurement with long fliping coil. Feb 16, ST #1 skew 18A 1A 13A 1A Variation of I1y (normal field) versus x. Wiggler #13 (8 Poles) magnetic measurement with a long flipping coil. Jan 6, ST Variation of I1y (normal field) versus x. Wiggler #1 (8 Poles) magnetic measurement with a long flipping coil. March 3, ST - - #13 norm 18A #1 norm 1A 13A 18A 1A 13A Variation of I1x with x, ( Skew field integral) Wiggler #13 (8Poles) magnetic measurement with long fliping coil. Jan 6, ST Variation of I1x with x, ( Skew field integral) Wiggler #1 (8Poles) magnetic measurement with long fliping coil. March 3, ST 1 #13 skew #1 skew 18A 1A 13A A 1A 13A -6-18A 1A 13A Variation of I1y (normal field) versus x. Wiggler #16 (8 Poles) magnetic measurement with a long flipping coil. March 16, ST #16 norm 18A 1A 13A Variation of I1x with x, ( Skew field integral) Wiggler #16 (8Poles) magnetic measurement with long fliping coil. March 16, ST 1 #16 skew Variation of I1y (normal field) versus x. Wiggler #9"prime" (8 Poles) magnetic measurement with a long flipping coil. March, ST #9' norm Variation of I1x with x, ( Skew field integral) Wiggler #9"prime" (8Poles) magnetic measurement with long fliping coil. March, ST 1 #9' skew A - A. Temnykh WIGGLE Workshop, Frascati A 1A 13A A - 18A 1A 1A A

36 Ring characterization with beam: tune plane mapping. Vertical beam size (vertical beam emittance) versus tune Frame 1 1 Feb Low fh, Pr = Frame 1 1 Feb CESRc, 9// xkhz tune scan, e+, pret OFF, RESONANCES DAMPED.67 Single beam tune scan Nov 7,.66 One SC wiggler optics.6.67 Single beam tune scan Sep, 1 SC wigglers optics Qx-Qs =.6 Qy.63 Qy Qx-Qv +Qs = CESRc working point Qx Qx Nov, One wiggler optics Sept, 1 wigglers optics with better tuned nonlinearities (Sextupoles and skew sextupoles) A. Temnykh WIGGLE Workshop, Frascati 36

CESR-c Wigglers. A. Temnykh for CESR operating group LEPP, Cornell University, Ithaca, NY 14850, USA

CESR-c Wigglers. A. Temnykh for CESR operating group LEPP, Cornell University, Ithaca, NY 14850, USA CESR-c Wigglers A. Temnykh for CESR operating group LEPP, Cornell University, Ithaca, NY 1485, USA D. Rice D. Rubin J. Crittenden S. Chapman J. Codner R. Gallagher Y. He J. Kandaswamy V. Medjidzade A.