An undulator for FELICITA I
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Nuclear Instruments and Methods in Physics Research A 341 (1994) ABS 9-ABS 10 North-Holland An undulator for FÉLICITA I T. Schmidt, F. Brinker, D. NHlle, Institute for Acceleratorphysics and Synchrotronradiation, Uniuersity ofDortmund, 44221 Dortmund, FRG FELICITA I is the first FEL experiment at the 1 .5 GeV dedicated synchrotron light source DELTA of the University of Dortmund, starting operation in the sum- mer of 1994 [1,2] . In the UV wavelength regime (400- 200 nm) the electromagnetic undulator will provide two operation modes, the optical klystron as well as a conventional FEL. The expected beam quality of DELTA [2] permits lasing even in the FEL mode which provides lower gain but, referring to the Renieri limit, higher output power and energy acceptance . Under the constraints of high flexibility, operation at electron energies above 500 MeV, a moderate K value, starting in the visible and use of the standard DELTA vacuum chamber, the FEL is designed with an electromagnetic planar undu- lator . The pole shape (Fig . la) is designed with POISSON and optimized for a low harmonic content . The pole width is calculated with the 3D code MAFIA. The iron yoke of the undulator is recycled from an old spec- trometer magnet of the University of Bonn . It consists of ten 1 m long, 30 cm width and 20 cm high blocks which are milled in house. The lower half is mounted on a girder on which cast iron is welded and milled. The sections are joined together in the middle of the pole where the flux lines are parallel . The precision is achieved with the help of fitting bolts. A precise gap is achieved by mounting the upper half top spacer right inside the gap (Figs . lb and lc). The coils for the undulator and dispersive section are just the same, 24 water cooled windings in 2 layers, 8 mm in square with a4 mm hole . To avoid field errors due to current drifts in FEL operation all coils are switched in series . The matching of the undulator section to let the first and second field integral vanish is done by separating some coils in the ratio 1 : 3. The 1/4, 3/4 matching forces the electrons to wiggle on * This work is supported by the Bundesministerium für Forschung und Technologie under contract 05 3PEAAI 0 . 0168-9002/94/$07 .00 © 1994 - Elsevier Science B.V . All rights reserved SSDI0168-9002(93)E0758-K NUCLEAR INSTRUMENTS &METHODS IN PHYSICS RESEARCH Section A nrs L2nUuuv~, utlr.l u~.nu_Ju Fig . 1 . (a) Pole shape, (b) crosssection and (c) side view with exitation pattern of the undulator. axis. In the OK mode the higher field in the dispersive section is realized just by connecting the middle coils to a stronger power supply. However, the saturation of the iron (0 .7 T on axis implies up to 2 T in iron) Table 1 Undulator parameters FÉLICITA I EXTENDED SYNOPSES Length 4.875 m Period length 25 cm Gap height 50 mm Operation mode FEL OK OK and disp Periods 17 7 1 K-value 2 .1 2 .1 16 .0 B 0 0 .09 T 0.09 T 0.7 T Current 83 A 83 A 670 A
Transcript of An undulator for FELICITA I
Nuclear Instruments and Methods in Physics Research A 341 (1994) ABS 9-ABS 10North-Holland
An undulator for FÉLICITA IT. Schmidt, F. Brinker, D. NHlle,Institute for Acceleratorphysics and Synchrotronradiation, Uniuersity ofDortmund, 44221 Dortmund, FRG
FELICITA I is the first FEL experiment at the 1.5GeV dedicated synchrotron light source DELTA of theUniversity of Dortmund, starting operation in the sum-mer of 1994 [1,2] . In the UV wavelength regime (400-200 nm) the electromagnetic undulator will providetwo operation modes, the optical klystron as well as aconventional FEL.
The expected beam quality of DELTA [2] permitslasing even in the FEL mode which provides lower gainbut, referring to the Renieri limit, higher output powerand energy acceptance . Under the constraints of highflexibility, operation at electron energies above 500MeV, a moderate K value, starting in the visible anduse of the standard DELTA vacuum chamber, theFEL is designed with an electromagnetic planar undu-lator .
The pole shape (Fig . la) is designed with POISSONand optimized for a low harmonic content. The polewidth is calculated with the 3D code MAFIA. The ironyoke of the undulator is recycled from an old spec-trometer magnet of the University of Bonn . It consistsof ten 1 m long, 30 cm width and 20 cm high blockswhich are milled in house. The lower half is mountedon a girder on which cast iron is welded and milled.The sections are joined together in the middle of thepole where the flux lines are parallel . The precision isachieved with the help of fitting bolts. A precise gap isachieved by mounting the upper half top spacer rightinside the gap (Figs. lb and lc).
The coils for the undulator and dispersive sectionare just the same, 24 water cooled windings in 2 layers,8 mm in square with a 4 mm hole . To avoid field errorsdue to current drifts in FEL operation all coils areswitched in series . The matching of the undulatorsection to let the first and second field integral vanishis done by separating some coils in the ratio 1 : 3. The1/4, 3/4 matching forces the electrons to wiggle on
* This work is supported by the Bundesministerium fürForschung und Technologie under contract 05 3PEAAI 0.
0168-9002/94/$07 .00 © 1994 - Elsevier Science B.V . All rights reservedSSDI0168-9002(93)E0758-K
NUCLEARINSTRUMENTS&METHODSIN PHYSICSRESEARCH
Section A
nrs L2nUuuv~, utlr.l u~.nu_Ju
Fig . 1 . (a) Pole shape, (b) crosssection and (c) side view withexitation pattern of the undulator.
axis. In the OK mode the higher field in the dispersivesection is realized just by connecting the middle coilsto a stronger power supply. However, the saturation ofthe iron (0 .7 T on axis implies up to 2 T in iron)
Table 1Undulator parameters FÉLICITA I
EXTENDED SYNOPSES
Length 4.875 mPeriod length 25 cmGap height 50 mmOperation mode FEL OK OK
and dispPeriods 17 7 1K-value 2.1 2.1 16 .0B0 0.09 T 0.09 T 0.7 TCurrent 83 A 83 A 670 A
ABS 10 T. Schmidt et al. I Nucl Instr. and Meth. i n Phys . Res A 341 (1994) ABS 9-ABS 10
requires additional power supplies for the matching .The correction of dispersive matching can be donewith the windings of the main coils not driven by theOK power supply. Every pole has a small coil forcorrections up to 3% of the undulator field.
The 0.09 T in the undulator section need 83 A (1 .6A/mm2 ) and about 50 V. In the dispersive section 0.7T require about 670 A (13 .2 A/mm2) by 45 V. Al-though water cooling for the undulator field is notnecesarry, it provides a higher flexibility of the undula-lor.
[11 D. Mile, A. Geisler, M. Ridder, T. Schmidt and K. Wille,these Proceedings (15th Int. Free Electron Laser Conf .,The Hague, The Netherlands, 1993) Nucl. Instr. and Meth .A 341 (1994) ABS 7
[21 DELTA Group, DELTA, a Status Report . University ofDortmund (1990) .
