FEL2012 - List of Authors (Kelly, R.N.)

Paper	Title	Page
WEPD68	UCLA Seeded THz FEL Undulator Buncher Design	527
	S.C. Gottschalk, R.N. Kelly STI, Washington, USA C. Joshi, S. Tochitsky UCLA, Los Angeles, California, USA S. Reiche PSI, Villigen PSI, Switzerland
	UCLA is planning to build a THz user facility. One is a seeded THz FEL tunable in the range of 0.5 - 3 THz or even 3-9 THz in an optical klystron configuration. Another* relies on microbunching at 340 micron using a 3.3 cm undulator or even driving the FEL with an electron beam from a laser-plasma accelerator. These FEL's make use of a 2.1m long pre-buncher, chicane and shorter, 110cm long radiator. Chicane requirements are modest. A round copper waveguide with 4.8mm ID will be used. We will describe the magnetic design and measured performance of the gap tunable undulators, mechanical design of the entire system, vacuum boxes, waveguides and expected operational approaches. Both undulators have 33mm periods and curved poles for two-plane focusing. Discussions will be included on issues associated with fabricating, sorting and shimming curved pole undulators. A new optimization method will be described that was used to meet magnetic requirements with a minimum volume of magnetic material. *S. Tochitsky et al, "Seeded FEL Microbunching Experiments at the UCLA Neptune Laboratory", Advanced Accelerator Conference 2010

THPD12	Design and Performance of the NLCTA-Echo 7 Undulators	571
	S.C. Gottschalk, R.N. Kelly, M.A. Offenbacker, J.F. Zumdieck STI, Washington, USA
	The Echo-enabled harmonic generation (EEHG) FEL at SLAC NLCTA has shown coherent radiation in the seventh harmonic (227 nm) of the second seed laser. Earlier experiments demonstrated 3rd and 4th EEHG. We describe design and performance of the 33mm and 55mm period undulators built by STI Optronics and used for these experiments. Magnetic design of the 33mm period undulator was based on an earlier curved pole, two-plane focusing undulator for the UCLA seeded THz FEL*. This design used an evolutionary optimizer and custom pre/post processing FEA codes to maximize field strength with minimum magnetic material while achieving specified two-plane focusing. The 55mm undulator was identical to the JLAB IR FEL and APS UA U55 designs. A challenge for both these devices was achieving tight normal and skew trajectory excursions (<500 G-cm²), zero trajectory offset and < 10 G-cm steering without end correctors over a 5mm diameter horizontal and vertical region with a 4 month delivery requirement. We will also describe a new tuning method based on operations research linear programming that was used to help meet these goals over a 2X larger region while maintaining 1 deg phase errors. D. Xiang et al, Phys. Rev. Let. 10⁸ 024802 (2012) D. Xiang et al, Phys. Rev. Let. 10⁵ 114801 (2010) * S. Gottschalk et al, "UCLA Seeded THz FEL Undulator-Buncher Design",this conference

THPD13	Design and Performance of the Wedged Pole Hybrid Undulator for the Fritz-Haber-Institut IR FEL	575
	S.C. Gottschalk, T.E. DeHart, R.N. Kelly, M.A. Offenbacker, A.S. Valla, J.F. Zumdieck STI, Washington, USA H. Bluem, D. Dowell, J. Rathke, A.M.M. Todd AES, Medford, NY, USA S. Gewinner, H. Junkes, G. Meijer, W. Schöllkopf, W.Q. Zhang FHI, Berlin, Germany U. Lehnert HZDR, Dresden, Germany
	An IR and THz FEL with a design wavelength range from 4 to 500 microns has been commissioned at the Fritz-Haber-Institut (FHI) in Berlin, Germany. Lasing at 28 MeV and a wavelength of 18 micron was achieved in Feb 2012. We describe the performance of the undulator built and installed at FHI by STI Optronics for use in the mid-IR range (< 50 micron) and 15-50 MeV beam energy. The undulator was a high field strength wedged pole hybrid (WPH) with 40mm period, 2.0m long, minimum gap 16.5mm. A new improvement was including radiation resistance in the magnetic design. We will discuss the measured magnetic and mechanical performance; central and zero steering/offset end field magnetic designs; key features of the mechanical design and gap adjustment system; new genetic shimming algorithms and local/EPICS control systems. W.Schöllkopf et al., "First Lasing of the IR FEL at the Fritz-Haber-Institut Berlin", this conference

Paper

Title

Page

UCLA Seeded THz FEL Undulator Buncher Design

527

S.C. Gottschalk, R.N. Kelly
STI, Washington, USA
C. Joshi, S. Tochitsky
UCLA, Los Angeles, California, USA
S. Reiche
PSI, Villigen PSI, Switzerland

UCLA is planning to build a THz user facility. One is a seeded THz FEL tunable in the range of 0.5 - 3 THz or even 3-9 THz in an optical klystron configuration. Another* relies on microbunching at 340 micron using a 3.3 cm undulator or even driving the FEL with an electron beam from a laser-plasma accelerator. These FEL's make use of a 2.1m long pre-buncher, chicane and shorter, 110cm long radiator. Chicane requirements are modest. A round copper waveguide with 4.8mm ID will be used. We will describe the magnetic design and measured performance of the gap tunable undulators, mechanical design of the entire system, vacuum boxes, waveguides and expected operational approaches. Both undulators have 33mm periods and curved poles for two-plane focusing. Discussions will be included on issues associated with fabricating, sorting and shimming curved pole undulators. A new optimization method will be described that was used to meet magnetic requirements with a minimum volume of magnetic material.
*S. Tochitsky et al, "Seeded FEL Microbunching Experiments at the UCLA Neptune Laboratory", Advanced Accelerator Conference 2010

THPD12

Design and Performance of the NLCTA-Echo 7 Undulators

571

S.C. Gottschalk, R.N. Kelly, M.A. Offenbacker, J.F. Zumdieck
STI, Washington, USA

The Echo-enabled harmonic generation (EEHG) FEL at SLAC NLCTA has shown coherent radiation in the seventh harmonic (227 nm) of the second seed laser*. Earlier experiments demonstrated 3rd and 4th EEHG**. We describe design and performance of the 33mm and 55mm period undulators built by STI Optronics and used for these experiments. Magnetic design of the 33mm period undulator was based on an earlier curved pole, two-plane focusing undulator for the UCLA seeded THz FEL***. This design used an evolutionary optimizer and custom pre/post processing FEA codes to maximize field strength with minimum magnetic material while achieving specified two-plane focusing. The 55mm undulator was identical to the JLAB IR FEL and APS UA U55 designs. A challenge for both these devices was achieving tight normal and skew trajectory excursions (<500 G-cm²), zero trajectory offset and < 10 G-cm steering without end correctors over a 5mm diameter horizontal and vertical region with a 4 month delivery requirement. We will also describe a new tuning method based on operations research linear programming that was used to help meet these goals over a 2X larger region while maintaining 1 deg phase errors.
*D. Xiang et al, Phys. Rev. Let. 10⁸ 024802 (2012)
**D. Xiang et al, Phys. Rev. Let. 10⁵ 114801 (2010)
*** S. Gottschalk et al, "UCLA Seeded THz FEL Undulator-Buncher Design",this conference

THPD13

Design and Performance of the Wedged Pole Hybrid Undulator for the Fritz-Haber-Institut IR FEL

575

S.C. Gottschalk, T.E. DeHart, R.N. Kelly, M.A. Offenbacker, A.S. Valla, J.F. Zumdieck
STI, Washington, USA
H. Bluem, D. Dowell, J. Rathke, A.M.M. Todd
AES, Medford, NY, USA
S. Gewinner, H. Junkes, G. Meijer, W. Schöllkopf, W.Q. Zhang
FHI, Berlin, Germany
U. Lehnert
HZDR, Dresden, Germany

An IR and THz FEL with a design wavelength range from 4 to 500 microns has been commissioned at the Fritz-Haber-Institut (FHI) in Berlin, Germany. Lasing at 28 MeV and a wavelength of 18 micron was achieved in Feb 2012*. We describe the performance of the undulator built and installed at FHI by STI Optronics for use in the mid-IR range (< 50 micron) and 15-50 MeV beam energy. The undulator was a high field strength wedged pole hybrid (WPH) with 40mm period, 2.0m long, minimum gap 16.5mm. A new improvement was including radiation resistance in the magnetic design. We will discuss the measured magnetic and mechanical performance; central and zero steering/offset end field magnetic designs; key features of the mechanical design and gap adjustment system; new genetic shimming algorithms and local/EPICS control systems.
*W.Schöllkopf et al., "First Lasing of the IR FEL at the Fritz-Haber-Institut Berlin", this conference