FEL2014 - List of Keywords (solenoid)

Paper	Title	Other Keywords	Page
THP003	Two Charges in the Same Bunch Train at the European XFEL	simulation, laser, operation, emittance	678
	Y.A. Kot, T. Limberg, I. Zagorodnov DESY, Hamburg, Germany
	The European XFEL has been initially designed for the operation with bunch charge of 1 nC () which was later extended down to 20 pC (). An important upgrade of this extension might be the ability to operate different bunch charges in the same RF pulse. In this paper we assume the nominal design of the XFEL injector which means in particular that both charges in the same RF pulse experience the same solenoid field and are generated by the laser of the same rms size. We discuss the requirements which the combined working points of the injector have to fulfil and show the results of the complete start to end (S2E) and SASE simulations for the simultaneous operation of 250 pC and 500 pC bunch charges. DESY XFEL Project Group "The European X-Ray Free-Electron Laser. Technical Design Report" July 2007 ** W. Decking and T. Limberg "European XFEL. Post-TDR Description" February 2013

THP011	Beam Measurement of Photocathode RF-gun for PAL-XFEL	laser, emittance, electron, gun	699
	J.H. Hong, M.S. Chae, J.H. Han, H.-S. Kang, C.-K. Min, S.J. Park, Y.J. Park PAL, Pohang, Kyungbuk, Republic of Korea I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea
	The Injector Test Facility (ITF) at Pohang Accelerator Laboratory (PAL) was constructed to develop an injector for the PAL X-ray free-electron laser (PAL-XFEL) project. The PAL-XFEL design requires the injector to produce an electron beam with a slice emittance of 0.4 mm-mrad at the charge of 200 pC. A 4-hole type RF-gun has been successfully fabricated and tested at ITF. In this paper we report the recent beam-measurement results using the RF-gun at ITF. Emittance measurements have been carried out by changing laser and RF parameters.

THP020	Electron Beam Dynamics Optimization Using A Unified Differential Evolution Algorithm	emittance, electron, controls, cavity	726
	J. Qiang, C.E. Mitchell LBNL, Berkeley, California, USA
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231. Accelerator beam dynamics design depends heavily on the use of control parameter optimization to achieve the best performance. In this paper, we report on electron beam dynamics optimization of a model photoinjector using a new unified differential evolution algorithm. We present the new unified differential evolution algorithm and benchmark its performance using several test examples. We also discuss the application of the algorithm in the multi-objective optimization of the photoinjector.

THP039	Commissioning of the Photo-Cathode RF Gun at APS	gun, cathode, laser, emittance	803
	Y.-E. Sun, J.C. Dooling, R.R. Lindberg, A. Nassiri, S.J. Pasky, H. Shang, T.L. Smith, A. Zholents ANL, Argonne, Ilinois, USA
	A S-band RF gun is recently RF conditioned and commissioned at APS, Argonne. In this paper we report the high-power RF conditioning process of the gun. Dark currents are monitored during the RF conditioning and found to be less than 150pC. Following the RF conditioning, photo-electron beams are generated from the gun and the copper cathode quantum efficiency is monitored. We study the quantum efficiency as gun gradient varies and vacuum condition improves. Photo-electron beam enery and emittance are measured as RF gun gradient and solenoid, as well as drive-laser conditions are varied. Finally we compare our experimental results with numerical simulations. Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

THP049	High Power RF Test and Analysis of Dark Current in the SwissFEL-gun	gun, cathode, laser, vacuum	843
	P. Craievich, S. Bettoni, M. Bopp, A. Citterio, C. Ozkan, M. Pedrozzi, J.-Y. Raguin, M. Schaer, A. Scherer, T. Schietinger, L. Stingelin PSI, Villigen PSI, Switzerland
	To fulfill the beam quality and operational requirements of the SwissFEL project, currently under construction at the Paul Scherrer Institut, a new RF photocathode gun for the electron source was designed and manufactured in house. A 2.6 cell S-band gun operating with near-perfect rotationally symmetric RF field was designed to operate with a 100MV/m cathode field at a repetition rate of 100Hz with average power dissipation of 0.9kW with pulse duration of 1us. The first SwissFEL-gun is now fabricated and installed in the SwissFEL Injector Test Facility (SITF). The frequency spectrum and field balance, through bead-pulling, have been directly verified in-situ and then the gun has been operated with high-power RF. The results of bead-pull measurements and high-power tests are presented and discussed. In addition the emitted dark current was also measured during the high-power tests and the charge within the RF pulse was measured as a function of the peak cathode field at different pulse durations. Faraday cup data were taken for cathode peak RF fields up to 100MV/m for the case of a diamond-turned polycrystalline copper cathode.

THP054	Dark Current Studies at the APEX Photoinjector	gun, cathode, simulation, electron	855
	R. Huang USTC/NSRL, Hefei, Anhui, People's Republic of China D. Filippetto, C. F. Papadopoulos, F. Sannibale LBNL, Berkeley, California, USA
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 The increasing scientific demand for a high repetition rate FEL light source is driving the development of electron sources with high beam quality, delivering electron bunches at rates in the MHz range. An ongoing project to develop such a source is the Advanced Photoinjector Experiment (APEX) at LBNL. High brightness electron beams require high fields at the cathode during the electron emission. Such high fields associated with imperfections on the cathode surface area can induce undesired electron field emission (dark current). Excessive dark current can generate quenching of SRF structures and undesired radiation doses activating accelerator components and damaging undulator structures. In the present paper, we discuss the dark current studies performed at APEX. Field emitters in the cathode area have been localized and characterized, and techniques for minimizing dark current emission and to passively remove it have been investigated.

THP061	Commissioning of an Improved Superconducting RF Photo Injector at ELBE	gun, SRF, cavity, laser	881
	J. Teichert, A. Arnold, M. Freitag, P.N. Lu, P. Michel, P. Murcek, H. Vennekate, R. Xiang HZDR, Dresden, Germany P. Kneisel JLab, Newport News, Virginia, USA I. Will MBI, Berlin, Germany
	In order to produce high-brightness electron beams in a superconducting RF photo injector, the most important point is to reach a high acceleration field in the cavity. For this reason two new 3.5-cell niobium cavities were fabricated, chemically treated and cleaned in collaboration with Jlab. The first of these two cavities was shipped to HZDR and assembled in a new cryomodule. This new gun (SRF Gun II) was installed in the ELBE accelerator hall in May 2014 and replaces the previous SRF Gun I. Beside the new cavity the ELBE SRF gun II differs from the previous gun by the integration of a superconducting solenoid. The paper presents the results of the first test run with a Cu photocathode.

Paper

Title

Other Keywords

Page

THP003

Two Charges in the Same Bunch Train at the European XFEL

simulation, laser, operation, emittance

678

Y.A. Kot, T. Limberg, I. Zagorodnov
DESY, Hamburg, Germany

The European XFEL has been initially designed for the operation with bunch charge of 1 nC (*) which was later extended down to 20 pC (**). An important upgrade of this extension might be the ability to operate different bunch charges in the same RF pulse. In this paper we assume the nominal design of the XFEL injector which means in particular that both charges in the same RF pulse experience the same solenoid field and are generated by the laser of the same rms size. We discuss the requirements which the combined working points of the injector have to fulfil and show the results of the complete start to end (S2E) and SASE simulations for the simultaneous operation of 250 pC and 500 pC bunch charges.
* DESY XFEL Project Group "The European X-Ray Free-Electron Laser. Technical Design Report" July 2007
** W. Decking and T. Limberg "European XFEL. Post-TDR Description" February 2013

THP011

Beam Measurement of Photocathode RF-gun for PAL-XFEL

laser, emittance, electron, gun

699

J.H. Hong, M.S. Chae, J.H. Han, H.-S. Kang, C.-K. Min, S.J. Park, Y.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea
I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea

The Injector Test Facility (ITF) at Pohang Accelerator Laboratory (PAL) was constructed to develop an injector for the PAL X-ray free-electron laser (PAL-XFEL) project. The PAL-XFEL design requires the injector to produce an electron beam with a slice emittance of 0.4 mm-mrad at the charge of 200 pC. A 4-hole type RF-gun has been successfully fabricated and tested at ITF. In this paper we report the recent beam-measurement results using the RF-gun at ITF. Emittance measurements have been carried out by changing laser and RF parameters.

THP020

Electron Beam Dynamics Optimization Using A Unified Differential Evolution Algorithm

emittance, electron, controls, cavity

726

J. Qiang, C.E. Mitchell
LBNL, Berkeley, California, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
Accelerator beam dynamics design depends heavily on the use of control parameter optimization to achieve the best performance. In this paper, we report on electron beam dynamics optimization of a model photoinjector using a new unified differential evolution algorithm. We present the new unified differential evolution algorithm and benchmark its performance using several test examples. We also discuss the application of the algorithm in the multi-objective optimization of the photoinjector.

THP039

Commissioning of the Photo-Cathode RF Gun at APS

gun, cathode, laser, emittance

803

Y.-E. Sun, J.C. Dooling, R.R. Lindberg, A. Nassiri, S.J. Pasky, H. Shang, T.L. Smith, A. Zholents
ANL, Argonne, Ilinois, USA

A S-band RF gun is recently RF conditioned and commissioned at APS, Argonne. In this paper we report the high-power RF conditioning process of the gun. Dark currents are monitored during the RF conditioning and found to be less than 150pC. Following the RF conditioning, photo-electron beams are generated from the gun and the copper cathode quantum efficiency is monitored. We study the quantum efficiency as gun gradient varies and vacuum condition improves. Photo-electron beam enery and emittance are measured as RF gun gradient and solenoid, as well as drive-laser conditions are varied. Finally we compare our experimental results with numerical simulations.
Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

THP049

High Power RF Test and Analysis of Dark Current in the SwissFEL-gun

gun, cathode, laser, vacuum

843

P. Craievich, S. Bettoni, M. Bopp, A. Citterio, C. Ozkan, M. Pedrozzi, J.-Y. Raguin, M. Schaer, A. Scherer, T. Schietinger, L. Stingelin
PSI, Villigen PSI, Switzerland

To fulfill the beam quality and operational requirements of the SwissFEL project, currently under construction at the Paul Scherrer Institut, a new RF photocathode gun for the electron source was designed and manufactured in house. A 2.6 cell S-band gun operating with near-perfect rotationally symmetric RF field was designed to operate with a 100MV/m cathode field at a repetition rate of 100Hz with average power dissipation of 0.9kW with pulse duration of 1us. The first SwissFEL-gun is now fabricated and installed in the SwissFEL Injector Test Facility (SITF). The frequency spectrum and field balance, through bead-pulling, have been directly verified in-situ and then the gun has been operated with high-power RF. The results of bead-pull measurements and high-power tests are presented and discussed. In addition the emitted dark current was also measured during the high-power tests and the charge within the RF pulse was measured as a function of the peak cathode field at different pulse durations. Faraday cup data were taken for cathode peak RF fields up to 100MV/m for the case of a diamond-turned polycrystalline copper cathode.

THP054

Dark Current Studies at the APEX Photoinjector

gun, cathode, simulation, electron

855

R. Huang
USTC/NSRL, Hefei, Anhui, People's Republic of China
D. Filippetto, C. F. Papadopoulos, F. Sannibale
LBNL, Berkeley, California, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The increasing scientific demand for a high repetition rate FEL light source is driving the development of electron sources with high beam quality, delivering electron bunches at rates in the MHz range. An ongoing project to develop such a source is the Advanced Photoinjector Experiment (APEX) at LBNL. High brightness electron beams require high fields at the cathode during the electron emission. Such high fields associated with imperfections on the cathode surface area can induce undesired electron field emission (dark current). Excessive dark current can generate quenching of SRF structures and undesired radiation doses activating accelerator components and damaging undulator structures. In the present paper, we discuss the dark current studies performed at APEX. Field emitters in the cathode area have been localized and characterized, and techniques for minimizing dark current emission and to passively remove it have been investigated.

THP061

Commissioning of an Improved Superconducting RF Photo Injector at ELBE

gun, SRF, cavity, laser

881

J. Teichert, A. Arnold, M. Freitag, P.N. Lu, P. Michel, P. Murcek, H. Vennekate, R. Xiang
HZDR, Dresden, Germany
P. Kneisel
JLab, Newport News, Virginia, USA
I. Will
MBI, Berlin, Germany

In order to produce high-brightness electron beams in a superconducting RF photo injector, the most important point is to reach a high acceleration field in the cavity. For this reason two new 3.5-cell niobium cavities were fabricated, chemically treated and cleaned in collaboration with Jlab. The first of these two cavities was shipped to HZDR and assembled in a new cryomodule. This new gun (SRF Gun II) was installed in the ELBE accelerator hall in May 2014 and replaces the previous SRF Gun I. Beside the new cavity the ELBE SRF gun II differs from the previous gun by the integration of a superconducting solenoid. The paper presents the results of the first test run with a Cu photocathode.