Electron gun jitter effects on beam bunching M. S. Liu and M. Iqbal Citation: Review of Scientific Instruments 85, 023303 (2014); doi: 10.1063/1.4866025 View online: http://dx.doi.org/10.1063/1.4866025 View Table of Contents: http://scitation.aip.org/content/aip/journal/rsi/85/2?ver=pdfcov Published by the AIP Publishing Articles you may be interested in A study of the effect of in-line and perpendicular magnetic fields on beam characteristics of electron guns in medical linear accelerators Med. Phys. 38, 4174 (2011); 10.1118/1.3600695 Subpicosecond jitter in picosecond electron bunches J. Vac. Sci. Technol. B 23, 196 (2005); 10.1116/1.1849212 Spatial and temporal diagnostics of a high-brightness electron beam by technique of laser Thomson scattering Rev. Sci. Instrum. 73, 1752 (2002); 10.1063/1.1461879 Measurement of electron bunch timing jitter using wakefield analysis Rev. Sci. Instrum. 71, 61 (2000); 10.1063/1.1150161 Self-bunching electron guns AIP Conf. Proc. 472, 875 (1999); 10.1063/1.58885
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 130.113.111.210 On: Wed, 24 Dec 2014 06:46:00
REVIEW OF SCIENTIFIC INSTRUMENTS 85, 023303 (2014)
Electron gun jitter effects on beam bunching M. S. Liu1 and M. Iqbal1,2,a) 1 2
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China Centre for High Energy Physics, University of the Punjab, Lahore 45590, Pakistan
(Received 14 September 2013; accepted 4 February 2014; published online 24 February 2014) For routine operation of Beijing Electron Positron Collider II (BEPCII) linac, many factors may affect the beam bunching process directly or indirectly. We present the measurements and analyses of the gun timing jitter, gun high voltage jitter, and beam energy at the exit of the standard acceleration section of the linac quantitatively. Almost 80 mV and more than 200 ps of gun high voltage and time jitters have ever been measured, respectively. It was analyzed that the gun timing jitter produced severe effects on beam energy than the gun high voltage jitter, if the timing jitter exceeded 100 ps which eventually deteriorates both the beam performance and the injection rate to the storage ring. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4866025] I. INTRODUCTION
As an injector, linac must have optimized beam performance including design and measured parameter.1 To obtain single bunch per beam pulse and increase the positron beam injection rate from the linac to the storage ring, a subharmonic bunching (SHB) system was installed on the Beijing Electron Positron Collider II (BEPCII) linear accelerator in 2006. Its stability is vital for the electron beam bunching and the beam injection rate from linac to the storage ring. The SHB system demands very high physical tolerance on the related hardware systems to obtain the best beam performance. The threshold values are 50 ps and 0.4%, for electron gun timing and high voltage jitters, respectively. Timing synchronization is very important which cause beam breakdown or beam instability. It includes gun timing and modulator timing, synchronization between the gun timing, SHB and buncher, and so on; all of these must be under control for the good beam performance.2 To obtain the positron, a tungsten target was struck by electron at 240 MeV and then it was captured and bunched by the capture section which is composed of high voltage power supply, several sets of focusing solenoids and a set of modulator.3 Therefore, any jitter from it would affect positron energy stability and its orbit. In routine operation, it was measured that high voltage power supply and several sets of focusing solenoids accuracy was less than 10−5 and the high voltage stability of modulator was ±0.1%.4 After the capture section, it was accelerated along the linac, 12 beam current transformers (BCTs) and 16 beam position monitors (BMPs) were installed to measure the beam current signals and beam position for positron and electron along the linac. Fig. 1 was positron orbit shown by the BPM whose jitter stability was less than 0.1 mm.5 The injection rate without jitter retained more than 60 mA/min. Since the electron is emitted from the electron gun, any jitter from it including its high voltage or timing may affect the beam energy stability, thus the machine operation status will deviate from the normal operation scenario. a) Author to whom correspondence should be addressed. Electronic mail:
[email protected] 0034-6748/2014/85(2)/023303/5/$30.00
Electron gun jitter is a much challenging for every accelerators laboratory around the world. Continuing efforts have been made to measure and reduce the jitters from the electron gun to maximize the beam stability. For the linac based FEL light source; the most serious issue was the beam arrival time jitter caused by the beam energy jitter in the injector. The beam energy jitter mainly resulted from the RF phase and amplitude of the gun. The jitter in both arrival time and energy at the end of the linac were reduced using velocity bunching scheme.6 For BNL electron gun system,7 jitter in the firing of the high voltage spark gap affected the energy of the pulse as well as the arrival time of the pulse at the cathode. This jitter was measured to be
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 130.113.111.210 On: Wed, 24 Dec 2014 06:46:00
REVIEW OF SCIENTIFIC INSTRUMENTS 85, 023303 (2014)
Electron gun jitter effects on beam bunching M. S. Liu1 and M. Iqbal1,2,a) 1 2
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China Centre for High Energy Physics, University of the Punjab, Lahore 45590, Pakistan
(Received 14 September 2013; accepted 4 February 2014; published online 24 February 2014) For routine operation of Beijing Electron Positron Collider II (BEPCII) linac, many factors may affect the beam bunching process directly or indirectly. We present the measurements and analyses of the gun timing jitter, gun high voltage jitter, and beam energy at the exit of the standard acceleration section of the linac quantitatively. Almost 80 mV and more than 200 ps of gun high voltage and time jitters have ever been measured, respectively. It was analyzed that the gun timing jitter produced severe effects on beam energy than the gun high voltage jitter, if the timing jitter exceeded 100 ps which eventually deteriorates both the beam performance and the injection rate to the storage ring. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4866025] I. INTRODUCTION
As an injector, linac must have optimized beam performance including design and measured parameter.1 To obtain single bunch per beam pulse and increase the positron beam injection rate from the linac to the storage ring, a subharmonic bunching (SHB) system was installed on the Beijing Electron Positron Collider II (BEPCII) linear accelerator in 2006. Its stability is vital for the electron beam bunching and the beam injection rate from linac to the storage ring. The SHB system demands very high physical tolerance on the related hardware systems to obtain the best beam performance. The threshold values are 50 ps and 0.4%, for electron gun timing and high voltage jitters, respectively. Timing synchronization is very important which cause beam breakdown or beam instability. It includes gun timing and modulator timing, synchronization between the gun timing, SHB and buncher, and so on; all of these must be under control for the good beam performance.2 To obtain the positron, a tungsten target was struck by electron at 240 MeV and then it was captured and bunched by the capture section which is composed of high voltage power supply, several sets of focusing solenoids and a set of modulator.3 Therefore, any jitter from it would affect positron energy stability and its orbit. In routine operation, it was measured that high voltage power supply and several sets of focusing solenoids accuracy was less than 10−5 and the high voltage stability of modulator was ±0.1%.4 After the capture section, it was accelerated along the linac, 12 beam current transformers (BCTs) and 16 beam position monitors (BMPs) were installed to measure the beam current signals and beam position for positron and electron along the linac. Fig. 1 was positron orbit shown by the BPM whose jitter stability was less than 0.1 mm.5 The injection rate without jitter retained more than 60 mA/min. Since the electron is emitted from the electron gun, any jitter from it including its high voltage or timing may affect the beam energy stability, thus the machine operation status will deviate from the normal operation scenario. a) Author to whom correspondence should be addressed. Electronic mail:
[email protected] 0034-6748/2014/85(2)/023303/5/$30.00
Electron gun jitter is a much challenging for every accelerators laboratory around the world. Continuing efforts have been made to measure and reduce the jitters from the electron gun to maximize the beam stability. For the linac based FEL light source; the most serious issue was the beam arrival time jitter caused by the beam energy jitter in the injector. The beam energy jitter mainly resulted from the RF phase and amplitude of the gun. The jitter in both arrival time and energy at the end of the linac were reduced using velocity bunching scheme.6 For BNL electron gun system,7 jitter in the firing of the high voltage spark gap affected the energy of the pulse as well as the arrival time of the pulse at the cathode. This jitter was measured to be
