IPAC2011 - Classification: 07 Accelerator Technology / T26 Low Level RF

Paper	Title	Page
MOPC097	LLRF Control System for PKU DC-SC Photocathode Injector	304
	H. Zhang, Y.M. Li, K.X. Liu, F. Wang, B.C. Zhang PKU/IHIP, Beijing, People's Republic of China
	A 1.3 GHz 3.5 Cell LG niobium cavity is installed for the new PKU DC-SC injector as its accelerating cavity with working temperature is 2K. High amplitude and phase stability is required for the updated SRF photocathode injector. This paper describes the design of Low Level RF control system based on FPGA, including hardware and software,and the communication function is realized by Tri-State Ethernet. The system should be operated on the precision with the amplitude of ±0.1% and phase stability of ±0.1°.

MOPC151	Design and Commissioning of a Multi-frequency Digital Low Level RF Control System*	433
	M. Konrad, U. Bonnes, C. Burandt, J. Conrad, R. Eichhorn, J. Enders, P.N. Nonn, N. Pietralla TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by DFG through CRC 634 and by the BMBF under 06 DA 9024 I. Triggered by the need to control the superconducting cavities of the S-DALINAC, which have a high loaded quality factor and are thus very susceptible to microphonics, the development of a digital low level RF control system was started. The chosen design proved to be very flexible since other frequencies than the original 3 GHz may be adapted easily: The system converts the RF signal coming from the cavity (e. g. 3 GHz) down to the base band using a hardware I/Q demodulator. The base band signals are digitized by ADCs and fed into a FPGA where the control algorithm is implemented. The resulting signals are I/Q modulated before they are sent back to the cavity. The superconducting cavities are operated with a self-excited loop algorithm whereas a generator-driven algorithm is used for the low Q normal-conducting bunching cavities. A 6 GHz RF front end allows the synchronous operation of a new 2f buncher at the S-DALINAC. Meanwhile, a 325 MHz version has been built to control a pulsed prototype test stand for the p-LINAC at FAIR. We will present the architecture of the RF control system as well as results obtained during operation.

MOPC152	Digital Control System for Solid State Direct Drive™ RF-Linacs	436
	J. Sirtl, M. Back, T. Kluge Siemens AG, Erlangen, Germany H. Schröder ASTRUM IT GmbH, Erlangen, Germany
	The Solid State Direct Drive™ concept for RF linacs has previously been introduced. Due to the different methodology (i.e. solid state based rather than electron tube based) as compared with conventional RF sources a new control system is required to deliver the required LLRF. To support this new technology a fully digital control system for this new concept has been developed. Progresses in Digital – Analogue Converter technology and FPGA technology allows us to create a digital System which works in the 150 Mhz baseband. The complete functionality was implemented in a Virtex 6 FPGA. Dispensing with the PLL allows an excellent jitter-behaviour. For this job, we use three 12 bit ADCs with a Sampling Rate of 1 GS/s and two 16 bit DACs (1 GS/s). The amplitude of the RF source is controlled by dividing the RF modules mounted on the power combiner* into two groups and controlling the relative phase of each group (in effect mimicking an “out-phasing” amplifier). This allows the modules to be operated at their optimum working point and allows a linear amplitude behaviour. * O. Heid, T. Hughes, Proc. of IPAC10, THPD002, p. 4278, Kyoto, Japan (2010). ** O. Heid, T. Hughes, Proc. of LINAC10, THPD068, Tsukuba, Japan.

MOPC153	Design and Implementation of Automatic Cavity Resonance Frequency Measurement and Tuning Procedure for FLASH and European XFEL Cryogenic Modules	439
	V. Ayvazyan, W. Koprek, D. Kostin, G. Kreps DESY, Hamburg, Germany Z. Geng SLAC, Menlo Park, California, USA
	The superconducting cavities in FLASH and European XFEL should be tuned to the frequency of 1.3 GHz after cool down and adjusted to initial frequency before warm up by stepper motor tuners. The initial frequency is 300 kHz far from the operating frequency (1.3 GHz) to remove mechanical hysteresis of the tuner. The cavities should be relaxed to initial frequency to avoid a plastically deformation. In framework of digital low level RF and DOOCS control systems we have developed a simple automatic procedure for the remote resonance frequency measurement and simultaneous remote tuning for all cavities which are driven from the single klystron. The basic idea is based on frequency sweeping both for driving klystron and for generation of local oscillator frequency with constant RF frequency from master oscillator. The developed system has been used during FLASH commissioning in spring 2010 and is in use for cavity and cryogenic module test stands for European XFEL at DESY.

MOPC154	RF Photo Gun Stability Measurement at PITZ	442
	I.I. Isaev, H.-J. Grabosch, M. Gross, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria M. Hoffmann, H. Schlarb DESY, Hamburg, Germany M.A. Khojoyan YerPhI, Yerevan, Armenia D. Richter HZB, Berlin, Germany A. Shapovalov NRNU MEPHI, Moscow, Russia I.H. Templin, I. Will MBI, Berlin, Germany
	The stability of the RF phase in the RF photo injector gun is one of the most important factors for the successful operation of linac based free-electron lasers. Instabilities in the RF launch phase can significantly reduce the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. The phase stability of the RF field is measured using the phase scan technique. Measurements were performed for different operating conditions at the Photo Injector Test facility at DESY, location Zeuthen (PITZ). Obtained stability measurement results will be presented and discussed.

MOPC155	Performance of the Micro-TCA Digital Feedback Board for DRFS Test at KEK-STF	445
	T. Miura, D.A. Arakawa, S. Fukuda, E. Kako, H. Katagiri, T. Matsumoto, S. Michizono, Y. Yano KEK, Ibaraki, Japan
	The test of distributed RF scheme (DRFS) for ILC was carried out at the superconducting RF test facility in KEK (KEK-STF). The LLRF system and two klystron units were installed in the same tunnel as SRF cavities. The vector-sum control for two cavities was done by using the micro-TCA digital feedback board. This board was the same one developed for the compact-ERL at KEK, but the software was changed for pulse operation. The result of the performance will be reported.

MOPC157	Performance of LLRF System at S1-Global in KEK*	451
	S. Michizono, D.A. Arakawa, S. Fukuda, E. Kako, H. Katagiri, T. Matsumoto, T. Miura, Y. Yano KEK, Ibaraki, Japan
	Vector-sum control was carried out at S1-Global. The rf stabilities of 0.007% in amplitude and 17 mdeg. in phase are obtained. Various diagnostics (such as on-line quench pulse detector, dynamic detuning monitor and so on) is implemented. The IF-mixture system, where 3 intermediate frequencies (IF) are used and the number of ADCs can be reduced, was used as rf waveform monitors. These monitors are used for the performance analysis. Quench phenomena observed at the high-gradient operation are also analyzed from the view point of dynamic change in loaded Q and cavity detuning during rf pulse.

MOPC158	RF Capture of a Beam with Charge-exchanging Multi-turn Injection	454
	T. Uesugi, Y. Ishi, Y. Kuriyama, J.-B. Lagrange, Y. Mori, R. Nakano, T. Planche, B. Qin, E. Yamakawa KURRI, Osaka, Japan Y. Niwa, K. Okabe, I. Sakai University of Fukui, Faculty of Engineering, Fukui, Japan
	Funding: This work was supported by MEXT of Japan in the framework of a task entitled ”Research and Development for an Accelerator-Driven Sub-critical System Using an FFAG Accelerator”. In the fixed field alternating gradient (FFAG) synchrotron in Kyoto university research reactor Institute (KURRI), charge exchange injection was adopted since 2011. The charge stripping foil is located on the closed orbit of the injection energy, and no bump orbit system is used. Instead, the injected beam escapes from the stripping foil according to the closed-orbit shift due to acceleration. In this scheme, it is important to minimize the number of foil hitting, which causes emittance growth and foil heating. In this paper, the rf capture is studied by means of simulation.

MOPC160	Digital LLRF for IFMIF-EVEDA	457
	A. Salom, A. Arriaga, J.C. Calvo, I. Kirpitchev, P. Méndez, D. Regidor, M. Weber CIEMAT, Madrid, Spain A. Mosnier CEA/IRFU, Gif-sur-Yvette, France F. Pérez CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
	The IFMIF-EVEDA project aims to build a prototype accelerator (deuteron, 9MeV, 125mA) to be located at Rokkasho, Japan, for design validation of the IFMIF Accelerator. CIEMAT from Madrid, Spain, is in charge of providing the RF systems for this prototype accelerator. The LLRF will adjust the phase and amplitude of the RF drive and the resonance frequency of the cavities. This paper summarizes its main characteristics and Control System integrated in EPICS. The hardware is based on a commercial FPGA board, an analog front end and a local timing system. Each LLRF system will control and diagnose two RF chains and it will handle the RF fast Interlocks (vacuum, arcs, reflected power and multipacting). A specific LLRF will be developed for the special case of the RFQ cavity, with one Master LLRF and three Slave LLRFs to feed the 8 RF chains of the cavity. The conceptual design and other capabilities of the system like automatic conditioning, frequency tuning for startup and field flatness of the RFQ, etc, will be shown in this paper together with the first low power test results of the LLRF prototype and the performance of the Control System.

MOPC161	Challenges for the Low Level RF Design for ESS	460
	A.J. Johansson Lund University, Lund, Sweden R. Zeng ESS, Lund, Sweden
	The European Spallation Source (ESS) is a planned neutron source to be built in Lund, Sweden, which is planned to produce the first neutrons in 2019. It will have an average beam power at the target of 5 MW, an average current along the Linac of 50 mA, and a pulse repetition rate and length of 20 Hz and 2 ms, respectively. The Linac will have around 200 LLRF stations employed to control a variety of RF cavities such as RFQ, DTL, spoke and elliptical superconducting cavities. The challenges on LLRF systems are mainly the high demands on energy efficiency on all parts of the facility, an operational goal of 95% availability of the facility and a comparably short time from start of final design to commissioning. Running with long pulses, high current and spoke cavities also brings new challenges on LLRF design. In this paper we will describe the consequences these challenges have on the LLRF system, and the proposed solutions and development projects that have started in order to reach these demands.

MOPC163	Low-level RF Control System for the Taiwan Photon Source	463
	M.-S. Yeh NSRRC, Hsinchu, Taiwan
	The low-level RF (LLRF) control system is an essential component of the RF system for Taiwan Photon Source. The LLRF control system will perform various functions including control loops for the cavity gap voltage and the phase feedback, RF system interlock protection and the diagnostics for a machine trip. The LLRF system is manufactured in house using the most recent commercial RF chips. The LLRF system has an analogue architecture similar to that used in the 1.5-GeV Taiwan Light Source (TLS). An overview of the system architecture and its functionality is presented herein.

MOPC164	Upgrade of the ISIS Synchrotron Low Power RF System	466
	A. Seville, N.E. Farthing, I.S.K. Gardner, R.J. Mathieson, J.W.G. Thomason STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom D.B. Allen STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
	The ISIS synchrotron at the Rutherford Appleton Laboratory in the UK now routinely uses a dual harmonic RF system to accelerate beam currents in excess of 230 uA to run two target stations simultaneously. In order to give more stable control of the phase of the RF voltage at each of the fundamental (1RF) and second harmonic (2RF) cavities, changes have been made to the low power RF (LPRF) control systems. In addition to this a new FPGA based master oscillator has been commissioned for the first time, and further changes using digital technologies to replace other components of the LPRF system are to be investigated. This paper reports on the LPRF hardware commissioning and reliability.

MOPC165	Digital Low Level RF Development at Daresbury Laboratory	469
	P.A. Corlett, L. Ma, A.J. Moss STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Digital LLRF development using Field Programmable Gate Arrays (FPGAs) is a new activity at Daresbury Laboratory. Using the LLRF4 development board, designed by Larry Doolittle of Lawrence Berkeley National Laboratory, a full featured control system incorporating fast feedback loops and a feed-forward system has been developed for use on the ALICE (Accelerators and Lasers in Combined Experiments) energy recovery linac. Technical details of the system are presented, along with experimental measurements.

MOPC166	Low RF Control Feedback and IQ Vector Modulator Compensation Functions	472
	M.G. Fedurin, R. Malone, V. Yakimenko BNL, Upton, Long Island, New York, USA
	IQ vector modulator is key element of the gun and linac RF control circuits at Accelerator Test Facility at Brookhaven National Laboratory. IQ modulator calibration procedure was developed to find proper compensation functions in the conversion algorithm to minimize phase-amplitude coupling and setting-reading errors: rms(A_set - A_read )= 0.03dB, rms(Phi_set - Phi_read) = 0.3 deg. Since stabilization of the RF phase and amplitude is become critical for many experiments the slow feedback was developed and applied as well to significantly compensate drifts in RF system.

Paper

Title

Page

LLRF Control System for PKU DC-SC Photocathode Injector

304

H. Zhang, Y.M. Li, K.X. Liu, F. Wang, B.C. Zhang
PKU/IHIP, Beijing, People's Republic of China

A 1.3 GHz 3.5 Cell LG niobium cavity is installed for the new PKU DC-SC injector as its accelerating cavity with working temperature is 2K. High amplitude and phase stability is required for the updated SRF photocathode injector. This paper describes the design of Low Level RF control system based on FPGA, including hardware and software,and the communication function is realized by Tri-State Ethernet. The system should be operated on the precision with the amplitude of ±0.1% and phase stability of ±0.1°.

MOPC151

Design and Commissioning of a Multi-frequency Digital Low Level RF Control System*

433

M. Konrad, U. Bonnes, C. Burandt, J. Conrad, R. Eichhorn, J. Enders, P.N. Nonn, N. Pietralla
TU Darmstadt, Darmstadt, Germany

Funding: Work supported by DFG through CRC 634 and by the BMBF under 06 DA 9024 I.
Triggered by the need to control the superconducting cavities of the S-DALINAC, which have a high loaded quality factor and are thus very susceptible to microphonics, the development of a digital low level RF control system was started. The chosen design proved to be very flexible since other frequencies than the original 3 GHz may be adapted easily: The system converts the RF signal coming from the cavity (e. g. 3 GHz) down to the base band using a hardware I/Q demodulator. The base band signals are digitized by ADCs and fed into a FPGA where the control algorithm is implemented. The resulting signals are I/Q modulated before they are sent back to the cavity. The superconducting cavities are operated with a self-excited loop algorithm whereas a generator-driven algorithm is used for the low Q normal-conducting bunching cavities. A 6 GHz RF front end allows the synchronous operation of a new 2f buncher at the S-DALINAC. Meanwhile, a 325 MHz version has been built to control a pulsed prototype test stand for the p-LINAC at FAIR. We will present the architecture of the RF control system as well as results obtained during operation.

MOPC152

Digital Control System for Solid State Direct Drive™ RF-Linacs

436

J. Sirtl, M. Back, T. Kluge
Siemens AG, Erlangen, Germany
H. Schröder
ASTRUM IT GmbH, Erlangen, Germany

The Solid State Direct Drive™ concept for RF linacs has previously been introduced*. Due to the different methodology (i.e. solid state based rather than electron tube based) as compared with conventional RF sources a new control system is required to deliver the required LLRF. To support this new technology a fully digital control system for this new concept has been developed. Progresses in Digital – Analogue Converter technology and FPGA technology allows us to create a digital System which works in the 150 Mhz baseband. The complete functionality was implemented in a Virtex 6 FPGA. Dispensing with the PLL allows an excellent jitter-behaviour. For this job, we use three 12 bit ADCs with a Sampling Rate of 1 GS/s and two 16 bit DACs (1 GS/s). The amplitude of the RF source is controlled by dividing the RF modules mounted on the power combiner** into two groups and controlling the relative phase of each group (in effect mimicking an “out-phasing” amplifier). This allows the modules to be operated at their optimum working point and allows a linear amplitude behaviour.
* O. Heid, T. Hughes, Proc. of IPAC10, THPD002, p. 4278, Kyoto, Japan (2010).
** O. Heid, T. Hughes, Proc. of LINAC10, THPD068, Tsukuba, Japan.

MOPC153

Design and Implementation of Automatic Cavity Resonance Frequency Measurement and Tuning Procedure for FLASH and European XFEL Cryogenic Modules

439

V. Ayvazyan, W. Koprek, D. Kostin, G. Kreps
DESY, Hamburg, Germany
Z. Geng
SLAC, Menlo Park, California, USA

The superconducting cavities in FLASH and European XFEL should be tuned to the frequency of 1.3 GHz after cool down and adjusted to initial frequency before warm up by stepper motor tuners. The initial frequency is 300 kHz far from the operating frequency (1.3 GHz) to remove mechanical hysteresis of the tuner. The cavities should be relaxed to initial frequency to avoid a plastically deformation. In framework of digital low level RF and DOOCS control systems we have developed a simple automatic procedure for the remote resonance frequency measurement and simultaneous remote tuning for all cavities which are driven from the single klystron. The basic idea is based on frequency sweeping both for driving klystron and for generation of local oscillator frequency with constant RF frequency from master oscillator. The developed system has been used during FLASH commissioning in spring 2010 and is in use for cavity and cryogenic module test stands for European XFEL at DESY.

MOPC154

RF Photo Gun Stability Measurement at PITZ

442

I.I. Isaev, H.-J. Grabosch, M. Gross, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany
M.A. Khojoyan
YerPhI, Yerevan, Armenia
D. Richter
HZB, Berlin, Germany
A. Shapovalov
NRNU MEPHI, Moscow, Russia
I.H. Templin, I. Will
MBI, Berlin, Germany

The stability of the RF phase in the RF photo injector gun is one of the most important factors for the successful operation of linac based free-electron lasers. Instabilities in the RF launch phase can significantly reduce the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. The phase stability of the RF field is measured using the phase scan technique. Measurements were performed for different operating conditions at the Photo Injector Test facility at DESY, location Zeuthen (PITZ). Obtained stability measurement results will be presented and discussed.

MOPC155

Performance of the Micro-TCA Digital Feedback Board for DRFS Test at KEK-STF

445

T. Miura, D.A. Arakawa, S. Fukuda, E. Kako, H. Katagiri, T. Matsumoto, S. Michizono, Y. Yano
KEK, Ibaraki, Japan

The test of distributed RF scheme (DRFS) for ILC was carried out at the superconducting RF test facility in KEK (KEK-STF). The LLRF system and two klystron units were installed in the same tunnel as SRF cavities. The vector-sum control for two cavities was done by using the micro-TCA digital feedback board. This board was the same one developed for the compact-ERL at KEK, but the software was changed for pulse operation. The result of the performance will be reported.

MOPC157

Performance of LLRF System at S1-Global in KEK*

451

S. Michizono, D.A. Arakawa, S. Fukuda, E. Kako, H. Katagiri, T. Matsumoto, T. Miura, Y. Yano
KEK, Ibaraki, Japan

Vector-sum control was carried out at S1-Global. The rf stabilities of 0.007% in amplitude and 17 mdeg. in phase are obtained. Various diagnostics (such as on-line quench pulse detector, dynamic detuning monitor and so on) is implemented. The IF-mixture system, where 3 intermediate frequencies (IF) are used and the number of ADCs can be reduced, was used as rf waveform monitors. These monitors are used for the performance analysis. Quench phenomena observed at the high-gradient operation are also analyzed from the view point of dynamic change in loaded Q and cavity detuning during rf pulse.

MOPC158

RF Capture of a Beam with Charge-exchanging Multi-turn Injection

454

T. Uesugi, Y. Ishi, Y. Kuriyama, J.-B. Lagrange, Y. Mori, R. Nakano, T. Planche, B. Qin, E. Yamakawa
KURRI, Osaka, Japan
Y. Niwa, K. Okabe, I. Sakai
University of Fukui, Faculty of Engineering, Fukui, Japan

Funding: This work was supported by MEXT of Japan in the framework of a task entitled ”Research and Development for an Accelerator-Driven Sub-critical System Using an FFAG Accelerator”.
In the fixed field alternating gradient (FFAG) synchrotron in Kyoto university research reactor Institute (KURRI), charge exchange injection was adopted since 2011. The charge stripping foil is located on the closed orbit of the injection energy, and no bump orbit system is used. Instead, the injected beam escapes from the stripping foil according to the closed-orbit shift due to acceleration. In this scheme, it is important to minimize the number of foil hitting, which causes emittance growth and foil heating. In this paper, the rf capture is studied by means of simulation.

MOPC160

Digital LLRF for IFMIF-EVEDA

457

A. Salom, A. Arriaga, J.C. Calvo, I. Kirpitchev, P. Méndez, D. Regidor, M. Weber
CIEMAT, Madrid, Spain
A. Mosnier
CEA/IRFU, Gif-sur-Yvette, France
F. Pérez
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain

The IFMIF-EVEDA project aims to build a prototype accelerator (deuteron, 9MeV, 125mA) to be located at Rokkasho, Japan, for design validation of the IFMIF Accelerator. CIEMAT from Madrid, Spain, is in charge of providing the RF systems for this prototype accelerator. The LLRF will adjust the phase and amplitude of the RF drive and the resonance frequency of the cavities. This paper summarizes its main characteristics and Control System integrated in EPICS. The hardware is based on a commercial FPGA board, an analog front end and a local timing system. Each LLRF system will control and diagnose two RF chains and it will handle the RF fast Interlocks (vacuum, arcs, reflected power and multipacting). A specific LLRF will be developed for the special case of the RFQ cavity, with one Master LLRF and three Slave LLRFs to feed the 8 RF chains of the cavity. The conceptual design and other capabilities of the system like automatic conditioning, frequency tuning for startup and field flatness of the RFQ, etc, will be shown in this paper together with the first low power test results of the LLRF prototype and the performance of the Control System.

MOPC161

Challenges for the Low Level RF Design for ESS

460

A.J. Johansson
Lund University, Lund, Sweden
R. Zeng
ESS, Lund, Sweden

The European Spallation Source (ESS) is a planned neutron source to be built in Lund, Sweden, which is planned to produce the first neutrons in 2019. It will have an average beam power at the target of 5 MW, an average current along the Linac of 50 mA, and a pulse repetition rate and length of 20 Hz and 2 ms, respectively. The Linac will have around 200 LLRF stations employed to control a variety of RF cavities such as RFQ, DTL, spoke and elliptical superconducting cavities. The challenges on LLRF systems are mainly the high demands on energy efficiency on all parts of the facility, an operational goal of 95% availability of the facility and a comparably short time from start of final design to commissioning. Running with long pulses, high current and spoke cavities also brings new challenges on LLRF design. In this paper we will describe the consequences these challenges have on the LLRF system, and the proposed solutions and development projects that have started in order to reach these demands.

MOPC163

Low-level RF Control System for the Taiwan Photon Source

463

M.-S. Yeh
NSRRC, Hsinchu, Taiwan

The low-level RF (LLRF) control system is an essential component of the RF system for Taiwan Photon Source. The LLRF control system will perform various functions including control loops for the cavity gap voltage and the phase feedback, RF system interlock protection and the diagnostics for a machine trip. The LLRF system is manufactured in house using the most recent commercial RF chips. The LLRF system has an analogue architecture similar to that used in the 1.5-GeV Taiwan Light Source (TLS). An overview of the system architecture and its functionality is presented herein.

MOPC164

Upgrade of the ISIS Synchrotron Low Power RF System

466

A. Seville, N.E. Farthing, I.S.K. Gardner, R.J. Mathieson, J.W.G. Thomason
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
D.B. Allen
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

The ISIS synchrotron at the Rutherford Appleton Laboratory in the UK now routinely uses a dual harmonic RF system to accelerate beam currents in excess of 230 uA to run two target stations simultaneously. In order to give more stable control of the phase of the RF voltage at each of the fundamental (1RF) and second harmonic (2RF) cavities, changes have been made to the low power RF (LPRF) control systems. In addition to this a new FPGA based master oscillator has been commissioned for the first time, and further changes using digital technologies to replace other components of the LPRF system are to be investigated. This paper reports on the LPRF hardware commissioning and reliability.

MOPC165

Digital Low Level RF Development at Daresbury Laboratory

469

P.A. Corlett, L. Ma, A.J. Moss
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Digital LLRF development using Field Programmable Gate Arrays (FPGAs) is a new activity at Daresbury Laboratory. Using the LLRF4 development board, designed by Larry Doolittle of Lawrence Berkeley National Laboratory, a full featured control system incorporating fast feedback loops and a feed-forward system has been developed for use on the ALICE (Accelerators and Lasers in Combined Experiments) energy recovery linac. Technical details of the system are presented, along with experimental measurements.

MOPC166

Low RF Control Feedback and IQ Vector Modulator Compensation Functions

472

M.G. Fedurin, R. Malone, V. Yakimenko
BNL, Upton, Long Island, New York, USA

IQ vector modulator is key element of the gun and linac RF control circuits at Accelerator Test Facility at Brookhaven National Laboratory. IQ modulator calibration procedure was developed to find proper compensation functions in the conversion algorithm to minimize phase-amplitude coupling and setting-reading errors: rms(A_set - A_read )= 0.03dB, rms(Phi_set - Phi_read) = 0.3 deg. Since stabilization of the RF phase and amplitude is become critical for many experiments the slow feedback was developed and applied as well to significantly compensate drifts in RF system.