IBIC2012 - Classification: Beam Charge and Current Monitors

Paper

Title

Page

Modeling and Performance Evaluation of DCCTs in SSRF

16

Z.C. Chen, Y.B. Leng, Y. Xiong, W.M. Zhou
SSRF, Shanghai, People's Republic of China

Direct Current Current Transformer (DCCT) is the most commonly used high precision current monitor in modern particle accelerators including Shanghai Synchrotron Radiation Facility (SSRF). Three types of noise have been observed in the output signal of the DCCT in the storage ring of SSRF: power line noise, beam current related narrow band noise and random square wave noise from nowhere. This article will discuss the noise removal algorithms in SSRF and the performance of the DCCTs afterwards.

Slides MOCB03 [1.436 MB]

MOCC03

The First Electron Bunch Measurement by means of DAST Organic EO Crystals

29

Y. Okayasu, S. Matsubara, T. Togashi
JASRI/SPring-8, Hyogo-ken, Japan
M. Aoyama
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada
The University of Tokyo, Tokyo, Japan
T. Matsukawa
RIKEN ASI, Sendai, Miyagi, Japan
H. Minamide
RIKEN Advanced Science Insititute, Sendai, Miyagi, Japan
K. Ogawa, T. Sato, H. Tomizawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
E. Takahashi
RIKEN, Saitama, Japan

Pilot user experiments via the seeded FEL have been demonstrated at the Prototype Test Accelerator (VUV-FEL), SPring-8 from July, 2012. A precise measurement of the electron bunch charge distribution (BCD) is crucial key to keep spatial and temporal overlaps between high-order harmonic (HH) laser pulses and electron bunches. R&D of the 3D-BCD monitor with a single-shot detection has been extensively promoted at SPring-8. The monitor adopts a spectral decoding based Electro-Optic (EO) sampling technique that is non-destructive and enables real-time reconstruction of the 3D-BCD with a temporal resolution of 30- to 40-fs (FWHM). So far, such EO sampling based BCD monitors have been developed by utilizing inorganic EO crystals such as ZnTe and their temporal resolutions are limited to ~130 fs (FWHM). As a part of this project, the first BCD measurement with an organic EO crystal DAST has been successfully demonstrated at the facility. Signal intensities, temporal resolutions and radiation related issues via both ZnTe and DAST are discussed.

Slides MOCC03 [3.912 MB]

MOPA04

An Electron Beam Profile Monitor for the Race-track Microtron

54

S.D. Dhole, V.N. Bhoraskar, B.J. Patil, N.S. Shinde
University of Pune, Pune, India

In electron irradiation experiments on materials such as semiconductors, solar cells etc., an uniformity and the charge distribution in the electron beam is very important. Therefore, an electron beam current monitor and its electronic system have been designed and built to measure the distribution of a beam current either in the horizontal or vertical direction along with the beam dimensions. To obtain X-Y beam profile, a special type of Faraday Cup was designed which mainly consists of charge collecting electrodes made up of thin copper strips. Each strip having dimensions 0.5 mm wide, 4 mm thick and 20 mm long were fixed parallel to each other and separation between them was ~ 0.5 mm. This multi electrode Faraday was mounted at the extraction port of the Race Track Microtron, where 1 MeV electron beam allowed to fall on it. The beam characterization in the form of current and uniformity were measured. The current from each strip were measured using an electronic circuit developed based on the multiplexing principle. The uniformity of the beam can be measured with an accuracy of 10%. The minimum and maximum dimensions which can be measured are 3 mm and 15 mm respectively.

MOPA06

VIMOS, New Capabilities for an Optical Safety System

57

K. Thomsen, J. Devlaminck
PSI, Villigen PSI, Switzerland

VIMOS is a dedicated safety system developed at the Spallation Neutron Source SINQ at the Paul Scherrer Institut, PSI, in Switzerland. VIMOS very directly monitors the correct current density distribution of the proton beam on the target by sampling the light emitted from a glowing mesh heated by the passing protons. The design has been optimized for obtaining maximum sensitivity and timely detection of beam irregularities relying on standard well-proven components. Recently it has been demonstrated that technical boundary conditions like radiation level and signal strength should allow for upgrading the system to a sensitive diagnostic device delivering quantitative and image-resolved values for the proton current density distribution on the SINQ target. By determining the temperature of the glowing mesh from the signals in two separate wavelength bands the temperature distribution over the mesh can be derived und subsequently the incident proton beam current density distribution. Work aimed at investigating the feasibility of adding these diagnostic abilities to VIMOS shows initial promising results. The status of the project and preliminary findings will be reported.

MOPA07

Development of a Phase Probe for the NIRS Small Cyclotron HM-18

60

S. Hojo, A. Goto, T. Honma, K. Katagiri, A. Sugiura
NIRS, Chiba-shi, Japan
Y. Takahashi
AEC, Chiba, Japan

The small cyclotron HM-18 of the National Institute of Radiological Sciences (NIRS) has been operated for use in RI production since 1994. The HM-18 allows us to accelerate protons and deuterons at fixed energies of 18 and 9 MeV, respectively. It has four trim coils for generation of the isochronous fields. Until recently, currents of the four trim coils had been adjusted only by monitoring the output beam intensity. In order to exactly produce the isochronous fields, a new phase probe has been installed in the HM-18. The phase probe has a simple structure in which four copper electrode plates of 60 mm x70 mm in area are glued to a copper base plate with a polyimide insulator between them. The thicknesses of the copper plates and the polyimide are 0.1 mm. This structure has an advantage that it can be easily installed in the cyclotron; only one part of a pair of upper and lower electrodes, which is usually adopted, is simply attached on the surface of the (lower) sector pole. The development of the phase probe and some results of a preliminary beam test using it are reported.

MOPA08

Various Usages of Wall Current Monitors for Commissioning of RF Systems in J-PARC Synchrotrons

63

F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
K. Hara, K. Hasegawa, C. Ohmori, M. Toda, M. Yoshii
KEK, Tokai, Ibaraki, Japan

Wall current monitors (WCM) for rf system commissioning are installed in the J-PARC synchrotrons, the RCS and the MR. The WCM signals are used as the input of the beam loading compensation system, and also used diagnosis to adjust the rf system parameters. Since the rf and beam frequency is in the range of a few MHz, direct measurement of the WCM signals is possible. For the diagnosis, the WCM signals are taken by an oscilloscope with the revolution clock signal generated by the LLRF control system, and slices of the WCM waveform with lengths of the revolution periods are generated. By stacking the slices, one can get a mountain plot, which shows motions of bunches and variations of the bunch shapes. Also, time variations of the bunching factor, which are important for acceleration of high intensity proton beams, are obtained. The harmonic analysis is performed on the WCM signal and the cavity voltage monitor signal. By using complex amplitudes of them, one can calculate the impedance seen by the beam. In this presentation, we show examples of the analyses described above. The rf parameters for high intensity beams have been successfully adjusted by using these analyses.

MOPB87

Development and First Tests of a High Sensitivity Charge Monitor for SwissFEL

287

S. Artinian, J.F. Bergoz, F. Stulle
BERGOZ Instrumentation, Saint Genis Pouilly, France
P. Pollet, V. Schlott
PSI, Villigen PSI, Switzerland

The compact X-ray free electron laser SwissFEL, which is presently under development at the Paul Scherrer Institut (PSI) in Villigen, Switzerland, will operate at comparably low charges, allowing the compression of the electron bunches to a few femto-seconds (nominal 200 pC mode) and even towards the atto-second range (short bunch 10 pC mode). A high precision charge measurement turns out to be a challenge, especially in the presence of dark currents, which may occur from high gradient RF gun and accelerating structure operation. In response to this challenge, a higher sensitivity charge transformer and new beam charge monitor electronics were developed in collaboration between Bergoz Instrumentation and PSI. The Turbo-ICT captures sub-pC bunch charge thanks to a new magnetic alloy exhibiting very low core loss. Transmission over a carrier using narrow-band cable television technique preserves the signal integrity from the Turbo-ICT to the BCM-RF. Electro-magnetic and RF interferences are strongly attenuated; the dark current signal is suppressed. First beam test results, which have been performed at the SwissFEL Test Injector Facility (STIF), are presented in this contribution.

TUPA05

The Calibration Factor Determined and Analysis for HLS Bunch Current Measurement System

334

Y.L. Yang, C. Cheng, P. Lu, T.J. Ma, B.G. Sun, J.G. Wang, J.Y. Zou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Work supported by National Natural Science Project(11105141) and Chinese Universities Scientific Fund
For bunch current measurement, the calibration factor is a key parameter. Usually, button electrode or stripline electrode can be selected as signal pickup, and peak value or integral of bunch signal from pickup can be used to calculate the related bunch current value. To obtain the absolute value of bunch current, the calibration factor should be determined with the help of DCCT. At HLS, the Stretch effect of bunch length was observed when bunch current decay over time and this will affect the performance of bunch current detection for different pickup type and calculate method. Theoretical analysis and experimental validation results are performed to find out an ideal solution for bunch current measurement at HLS. The results show that, bunch current measurement system can obtain the best performance by stripline and its integral signal.

TUPA06

Pulsed Electron Beam Current and Flux Monitor for the Race-track Microtron

337

S.D. Dhole, S. Akhter, V.N. Bhoraskar, B.J. Patil, N.S. Shinde
University of Pune, Pune, India

In electron irradiation experiments on the materials, a true current of the electron beam is to be known to calculate the electron fluence received by the sample. Therefore, a pulsed electron beam current and flux monitor alongwith electronic system for an electron accelerator called Race-Track Microtron has been designed and developed. The sensing device used was a ferrite core having suitable number of turns of copper wire wound around it, through which the electron beam was passed without loss in the intensity. With an appropriate developed electronic circuit, the instantaneous value of the induced voltage was measured which in turn provides value of the electron beam pulsed current. The total charge passed through the ferrite core per unit time was therefore recorded and an integrated value of the total charge in a given period could be derived. This system can be used to measure the electron flux in the range from 10⁸ electron/cm² to 10¹⁶ electron/cm². Moreover, this system has been used successfully in a few electron irradiation experiments where the knowledge of the electron fluence received by the sample is required.

TUPA07

BPM Selection for Beam Current Monitoring in SSRF

341

Z.C. Chen, Y.B. Leng, Y.B. Yan
SSRF, Shanghai, People's Republic of China

Although Direct Current Current Transformer (DCCT) is the general solution of beam current monitor, Beam Position Monitor (BPM) sum signals may still surpass it in some aspects such as the faster data rate and higher resolution in low current situations. Nevertheless, an additional monitor should be harmless. Meanwhile, the DCCTs in the storage ring of Shanghai Synchrotron Radiation Facility (SSRF) have been suffering from various noise and the signals from the BPMs could be an aid to provide the beam current more accurately. There're 140 BPMs in the storage ring in SSRF but not all of them are suitable for this particular usage. This article focuses on the methods used here to dynamicly choose the BPMs that meet the criteria.

Paper	Title	Page
MOCB03	Modeling and Performance Evaluation of DCCTs in SSRF	16
	Z.C. Chen, Y.B. Leng, Y. Xiong, W.M. Zhou SSRF, Shanghai, People's Republic of China
	Direct Current Current Transformer (DCCT) is the most commonly used high precision current monitor in modern particle accelerators including Shanghai Synchrotron Radiation Facility (SSRF). Three types of noise have been observed in the output signal of the DCCT in the storage ring of SSRF: power line noise, beam current related narrow band noise and random square wave noise from nowhere. This article will discuss the noise removal algorithms in SSRF and the performance of the DCCTs afterwards.
	Slides MOCB03 [1.436 MB]

MOCC03	The First Electron Bunch Measurement by means of DAST Organic EO Crystals	29
	Y. Okayasu, S. Matsubara, T. Togashi JASRI/SPring-8, Hyogo-ken, Japan M. Aoyama JAEA/Kansai, Kyoto, Japan A. Iwasaki, S. Owada The University of Tokyo, Tokyo, Japan T. Matsukawa RIKEN ASI, Sendai, Miyagi, Japan H. Minamide RIKEN Advanced Science Insititute, Sendai, Miyagi, Japan K. Ogawa, T. Sato, H. Tomizawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan E. Takahashi RIKEN, Saitama, Japan
	Pilot user experiments via the seeded FEL have been demonstrated at the Prototype Test Accelerator (VUV-FEL), SPring-8 from July, 2012. A precise measurement of the electron bunch charge distribution (BCD) is crucial key to keep spatial and temporal overlaps between high-order harmonic (HH) laser pulses and electron bunches. R&D of the 3D-BCD monitor with a single-shot detection has been extensively promoted at SPring-8. The monitor adopts a spectral decoding based Electro-Optic (EO) sampling technique that is non-destructive and enables real-time reconstruction of the 3D-BCD with a temporal resolution of 30- to 40-fs (FWHM). So far, such EO sampling based BCD monitors have been developed by utilizing inorganic EO crystals such as ZnTe and their temporal resolutions are limited to ~130 fs (FWHM). As a part of this project, the first BCD measurement with an organic EO crystal DAST has been successfully demonstrated at the facility. Signal intensities, temporal resolutions and radiation related issues via both ZnTe and DAST are discussed.
	Slides MOCC03 [3.912 MB]

MOPA04	An Electron Beam Profile Monitor for the Race-track Microtron	54
	S.D. Dhole, V.N. Bhoraskar, B.J. Patil, N.S. Shinde University of Pune, Pune, India
	In electron irradiation experiments on materials such as semiconductors, solar cells etc., an uniformity and the charge distribution in the electron beam is very important. Therefore, an electron beam current monitor and its electronic system have been designed and built to measure the distribution of a beam current either in the horizontal or vertical direction along with the beam dimensions. To obtain X-Y beam profile, a special type of Faraday Cup was designed which mainly consists of charge collecting electrodes made up of thin copper strips. Each strip having dimensions 0.5 mm wide, 4 mm thick and 20 mm long were fixed parallel to each other and separation between them was ~ 0.5 mm. This multi electrode Faraday was mounted at the extraction port of the Race Track Microtron, where 1 MeV electron beam allowed to fall on it. The beam characterization in the form of current and uniformity were measured. The current from each strip were measured using an electronic circuit developed based on the multiplexing principle. The uniformity of the beam can be measured with an accuracy of 10%. The minimum and maximum dimensions which can be measured are 3 mm and 15 mm respectively.

MOPA06	VIMOS, New Capabilities for an Optical Safety System	57
	K. Thomsen, J. Devlaminck PSI, Villigen PSI, Switzerland
	VIMOS is a dedicated safety system developed at the Spallation Neutron Source SINQ at the Paul Scherrer Institut, PSI, in Switzerland. VIMOS very directly monitors the correct current density distribution of the proton beam on the target by sampling the light emitted from a glowing mesh heated by the passing protons. The design has been optimized for obtaining maximum sensitivity and timely detection of beam irregularities relying on standard well-proven components. Recently it has been demonstrated that technical boundary conditions like radiation level and signal strength should allow for upgrading the system to a sensitive diagnostic device delivering quantitative and image-resolved values for the proton current density distribution on the SINQ target. By determining the temperature of the glowing mesh from the signals in two separate wavelength bands the temperature distribution over the mesh can be derived und subsequently the incident proton beam current density distribution. Work aimed at investigating the feasibility of adding these diagnostic abilities to VIMOS shows initial promising results. The status of the project and preliminary findings will be reported.

MOPA07	Development of a Phase Probe for the NIRS Small Cyclotron HM-18	60
	S. Hojo, A. Goto, T. Honma, K. Katagiri, A. Sugiura NIRS, Chiba-shi, Japan Y. Takahashi AEC, Chiba, Japan
	The small cyclotron HM-18 of the National Institute of Radiological Sciences (NIRS) has been operated for use in RI production since 1994. The HM-18 allows us to accelerate protons and deuterons at fixed energies of 18 and 9 MeV, respectively. It has four trim coils for generation of the isochronous fields. Until recently, currents of the four trim coils had been adjusted only by monitoring the output beam intensity. In order to exactly produce the isochronous fields, a new phase probe has been installed in the HM-18. The phase probe has a simple structure in which four copper electrode plates of 60 mm x70 mm in area are glued to a copper base plate with a polyimide insulator between them. The thicknesses of the copper plates and the polyimide are 0.1 mm. This structure has an advantage that it can be easily installed in the cyclotron; only one part of a pair of upper and lower electrodes, which is usually adopted, is simply attached on the surface of the (lower) sector pole. The development of the phase probe and some results of a preliminary beam test using it are reported.

MOPA08	Various Usages of Wall Current Monitors for Commissioning of RF Systems in J-PARC Synchrotrons	63
	F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan K. Hara, K. Hasegawa, C. Ohmori, M. Toda, M. Yoshii KEK, Tokai, Ibaraki, Japan
	Wall current monitors (WCM) for rf system commissioning are installed in the J-PARC synchrotrons, the RCS and the MR. The WCM signals are used as the input of the beam loading compensation system, and also used diagnosis to adjust the rf system parameters. Since the rf and beam frequency is in the range of a few MHz, direct measurement of the WCM signals is possible. For the diagnosis, the WCM signals are taken by an oscilloscope with the revolution clock signal generated by the LLRF control system, and slices of the WCM waveform with lengths of the revolution periods are generated. By stacking the slices, one can get a mountain plot, which shows motions of bunches and variations of the bunch shapes. Also, time variations of the bunching factor, which are important for acceleration of high intensity proton beams, are obtained. The harmonic analysis is performed on the WCM signal and the cavity voltage monitor signal. By using complex amplitudes of them, one can calculate the impedance seen by the beam. In this presentation, we show examples of the analyses described above. The rf parameters for high intensity beams have been successfully adjusted by using these analyses.

MOPB87	Development and First Tests of a High Sensitivity Charge Monitor for SwissFEL	287
	S. Artinian, J.F. Bergoz, F. Stulle BERGOZ Instrumentation, Saint Genis Pouilly, France P. Pollet, V. Schlott PSI, Villigen PSI, Switzerland
	The compact X-ray free electron laser SwissFEL, which is presently under development at the Paul Scherrer Institut (PSI) in Villigen, Switzerland, will operate at comparably low charges, allowing the compression of the electron bunches to a few femto-seconds (nominal 200 pC mode) and even towards the atto-second range (short bunch 10 pC mode). A high precision charge measurement turns out to be a challenge, especially in the presence of dark currents, which may occur from high gradient RF gun and accelerating structure operation. In response to this challenge, a higher sensitivity charge transformer and new beam charge monitor electronics were developed in collaboration between Bergoz Instrumentation and PSI. The Turbo-ICT captures sub-pC bunch charge thanks to a new magnetic alloy exhibiting very low core loss. Transmission over a carrier using narrow-band cable television technique preserves the signal integrity from the Turbo-ICT to the BCM-RF. Electro-magnetic and RF interferences are strongly attenuated; the dark current signal is suppressed. First beam test results, which have been performed at the SwissFEL Test Injector Facility (STIF), are presented in this contribution.

TUPA05	The Calibration Factor Determined and Analysis for HLS Bunch Current Measurement System	334
	Y.L. Yang, C. Cheng, P. Lu, T.J. Ma, B.G. Sun, J.G. Wang, J.Y. Zou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Work supported by National Natural Science Project(11105141) and Chinese Universities Scientific Fund For bunch current measurement, the calibration factor is a key parameter. Usually, button electrode or stripline electrode can be selected as signal pickup, and peak value or integral of bunch signal from pickup can be used to calculate the related bunch current value. To obtain the absolute value of bunch current, the calibration factor should be determined with the help of DCCT. At HLS, the Stretch effect of bunch length was observed when bunch current decay over time and this will affect the performance of bunch current detection for different pickup type and calculate method. Theoretical analysis and experimental validation results are performed to find out an ideal solution for bunch current measurement at HLS. The results show that, bunch current measurement system can obtain the best performance by stripline and its integral signal.

TUPA06	Pulsed Electron Beam Current and Flux Monitor for the Race-track Microtron	337
	S.D. Dhole, S. Akhter, V.N. Bhoraskar, B.J. Patil, N.S. Shinde University of Pune, Pune, India
	In electron irradiation experiments on the materials, a true current of the electron beam is to be known to calculate the electron fluence received by the sample. Therefore, a pulsed electron beam current and flux monitor alongwith electronic system for an electron accelerator called Race-Track Microtron has been designed and developed. The sensing device used was a ferrite core having suitable number of turns of copper wire wound around it, through which the electron beam was passed without loss in the intensity. With an appropriate developed electronic circuit, the instantaneous value of the induced voltage was measured which in turn provides value of the electron beam pulsed current. The total charge passed through the ferrite core per unit time was therefore recorded and an integrated value of the total charge in a given period could be derived. This system can be used to measure the electron flux in the range from 10⁸ electron/cm² to 10¹⁶ electron/cm². Moreover, this system has been used successfully in a few electron irradiation experiments where the knowledge of the electron fluence received by the sample is required.

TUPA07	BPM Selection for Beam Current Monitoring in SSRF	341
	Z.C. Chen, Y.B. Leng, Y.B. Yan SSRF, Shanghai, People's Republic of China
	Although Direct Current Current Transformer (DCCT) is the general solution of beam current monitor, Beam Position Monitor (BPM) sum signals may still surpass it in some aspects such as the faster data rate and higher resolution in low current situations. Nevertheless, an additional monitor should be harmless. Meanwhile, the DCCTs in the storage ring of Shanghai Synchrotron Radiation Facility (SSRF) have been suffering from various noise and the signals from the BPMs could be an aid to provide the beam current more accurately. There're 140 BPMs in the storage ring in SSRF but not all of them are suitable for this particular usage. This article focuses on the methods used here to dynamicly choose the BPMs that meet the criteria.