Publications by Douglas Bett


Compensation of orbit distortion due to quadrupole motion using feed-forward control at KEK ATF

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Elsevier 895 (2018) 10-18

C Charrondiere, M Pateki, S Kuroda, T Naito, P Burrows, N Terunuma, GB Christian, C Perry, D Bett, J Pfingstner, D Schulte, R Tomas, A Jeremie, K Kubo, T Okugi, T Tauchi

The high luminosity requirement for a future linear collider sets a demanding limit on the beam quality at the Interaction Point (IP). One potential source of luminosity loss is the motion of the ground itself. The resulting misalignments of the quadrupole magnets cause distortions to the beam orbit and hence an increase in the beam emittance. This paper describes a technique for compensating this orbit distortion by using seismometers to monitor the misalignment of the quadrupole magnets in real-time. The first demonstration of the technique was achieved at the Accelerator Test Facility (ATF) at KEK in Japan. The feed-forward system consisted of a seismometer-based quadrupole motion monitoring system, an FPGA-based feed-forward processor and a stripline kicker plus associated electronics. Through the application of a kick calculated from the position of a single quadruple, the system was able to remove about 80% of the component of the beam jitter that was correlated to the motion of the quadrupole. As a significant fraction of the orbit jitter in the ATF final focus is due to sources other than quadrupole misalignment, this amounted to an approximately 15% reduction in the absolute beam jitter.


Bunch-by-bunch position and angle stabilisation at ATF based on sub-micron resolution stripline beam position monitors

IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference (2016) 3859-3861

NB Kraljevic, RM Bodenstein, T Bromwich, PN Burrows, GB Christian, MR Davis, C Perry, R Ramjiawan, DR Bett

Copyright © 2016 CC-BY-3.0 and by the respective authors. A low-latency, sub-micron resolution stripline beam position monitoring (BPM) system has been developed and tested with beam at the KEK Accelerator Test Facility (ATF2), where it has been used to drive a beam stabilisation system. The fast analogue front-end signal processor is based on a single-stage radio-frequency down-mixer, with a measured latency of 16 ns and a demonstrated single-pass beam position resolution of below 300 nm using a beam with a bunch charge of approximately 1 nC. The BPM position data are digitised on a digital feedback board which is used to drive a pair of kickers local to the BPMs and nominally orthogonal in phase in closed-loop feedback mode, thus achieving both beam position and angle stabilisation. We report the reduction in jitter as measured at a witness stripline BPM located 30 metres downstream of the feedback system and its propagation to the AT F interaction point.


Development of a low-latency, micrometre-level precision, intra-train beam feedback system based on cavity beam position monitors

IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference (2016) 3862-3864

NB Kraljevic, RM Bodenstein, T Bromwich, PN Burrows, GB Christian, MR Davis, C Perry, R Ramjiawan, DR Bett

Copyright © 2016 CC-BY-3.0 and by the respective authors. A low-latency, intra-train, beam feedback system utilising a cavity beam position monitor (BPM) has been developed and tested at the final focus of the Accelerator Test Facility (ATF2) at KEK. A low-Q cavity BPM was utilised with custom signal processing electronics, designed for low latency and optimal position resolution, to provide an input beam position signal to the feedback system. A custom stripline kicker and power amplifier, and a digital feedback board, were used to provide beam correction and feedback control, respectively. The system was deployed in single-pass, multi-bunch mode with the aim of demonstrating intra-train beam stabilisation on electron bunches of charge ∼1 nC separated in time by c. 220 ns. The system has been used to demonstrate beam stabilisation to below the 75 nm level. Results of the latest beam tests, aimed at even higher performance, will be presented.


Design, testing and performance results of a high-resolution, broad-band, low-latency stripline beam position monitor system

6th International Particle Accelerator Conference, IPAC 2015 (2015) 1136-1138

NB Kraljevic, DR Bett, T Bromwich, PN Burrows, GB Christian, MR Davis, C Perry

Copyright © 2015 CC-BY-3.0 and by the respective authors. A high-resolution, low-latency beam position monitor (BPM) system has been developed for use in particle accelerators and beamlines that operate with trains of particle bunches with bunch separations as low as several tens of nanoseconds, such as future linear electronpositron colliders and free-electron lasers. The system was tested with electron beams in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan. The fast analogue front-end signal processor is based on a single-stage RF down-mixer. The processor latency is 15.6 +-0.1 ns. A position resolution below 300 nm has been demonstrated for beam intensities of around 1 nC, with single-pass beam.


Progress towards electron-beam feedback at the nanometre level at the Accelerator Test Facility (ATF2) at KEK

6th International Particle Accelerator Conference, IPAC 2015 (2015) 1133-1135

NB Kraljevic, DR Bett, T Bromwich, PN Burrows, GB Christian, MR Davis, C Perry

Copyright © 2015 CC-BY-3.0 and by the respective authors. Ultra-low latency beam-based digital feedbacks have been developed by the Feedback On Nanosecond Timescales (FONT) Group and tested at the Accelerator Test Facility (ATF2) at KEK in a programme aimed at beam stabilisation at the nanometre level at the ATF2 final focus. Three prototypes were tested: 1) A feedback system based on high-resolution stripline BPMs was used to stabilise the beam orbit in the beamline region c. 50m upstream of the final focus. 2) Information from this system was used in a feed-forward mode to stabilise the beam locally at the final focus. 3) A final-focus local feedback system utilising cavity BPMs was deployed. In all three cases the degree of beam stabilisation was observed in high-precision cavity BPMs at the ATF2 interaction point. Latest results are reported on stabilising the beam position to below 100 nanometres.


Status of ATF2 IP-BPM project

6th International Particle Accelerator Conference, IPAC 2015 (2015) 777-780

OR Blanco, P Bambade, F Bogard, P Cornebise, S Wallon, N Blaskovic Kraljevic, DR Bett, T Bromwich, PN Burrows, GB Christian, C Perry, S Araki, Y Honda, K Kubo, S Kuroda, T Naito, T Okugi, T Tauchi, N Terunuma, ES Kim, S Jang

Copyright © 2015 CC-BY-3.0 and by the respective authors. The efforts during the second half of 2014 towards nanometric beam position measurement and stabilization at the Interaction Point (IP) section of the Accelerator Test Facility (ATF) at KEK are presented. Recent improvements to the beam position monitor (BPM) data analysis and processing electronics, as well as the installation of a new set of C-Band BPMs, are reviewed.


Design and performance of a high resolution, low latency stripline beam position monitor system

PHYSICAL REVIEW SPECIAL TOPICS-ACCELERATORS AND BEAMS 18 (2015) ARTN 032803

RJ Apsimon, DR Bett, NB Kraljevic, PN Burrows, GB Christian, CI Clarke, BD Constance, HD Khah, MR Davis, C Perry, JR Lopez, CJ Swinson


Development of a low-latency, high-precision, intra-train beam feedback system based on cavity beam position monitors

IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference (2014) 2783-2785

N Blaskovic Kraljevic, DR Bett, PN Burrows, GB Christian, MR Davis, YI Kim, C Perry

Copyright © 2014 CC-BY-3.0 and by the respective authors. A low-latency, intra-train, beam feedback system utilising a cavity beam position monitor (BPM) has been developed and tested at the final focus of the Accelerator Test Facility (ATF2) at KEK. A low-Q cavity BPM was utilised with custom signal processing electronics, designed for low latency and optimal position resolution, to provide an input beam position signal to the feedback system. A custom stripline kicker and power amplifier, and an FPGA-based digital feedback board, were used to provide beam correction and feedback control, respectively. The system was deployed in single-pass, multi-bunch mode with the aim of demonstrating intratrain beam stabilisation on electron bunches of charge ∼1 nC separated in time by c. 280 ns. The system has been used to demonstrate beam stabilisation to below the 100 nm level. Results of the latest beam tests, aimed at even higher performance, will be presented.


Status of the CLIC-UK R&D programme on design of key systems for the compact linear collider

IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference (2014) 1354-1357

JA Clarke, N Collomb, SP Jamison, PA McIntosh, BJA Shepherd, G Stokes, R Corsini, A Grudiev, A Latina, T Lefevre, C Marrelli, M Modena, H Schmickler, D Schulte, P Skowronski, S Stapnes, F Tecker, R Tomas, R Wegner, M Wendt, W Wuensch, WA Gillespie, R Pan, MA Tyrk, DA Walsh, DR Bett, N Blaskovic Kraljevic, PN Burrows, GB Christian, L Corner, MR Davis, D Gamba, C Perry, J Roberts, R Ainsworth, T Aumeyr, L Bobb, S Boogert, A Bosco, FJ Cullinan, P Karataev, K Kruchinin, A Lyapin, LJ Nevay, J Snuverink, JR Towler, G Burt, A Dexter, M Jenkins, S Karimian, C Lingwood, B Woolley, R Jones, AV Praveen Kumar

Copyright © 2014 CC-BY-3.0 and by the respective authors. Six UK institutes are engaged in a collaborative R&D programme with CERN aimed at demonstrating key aspects of technology feasibility for the Compact Linear Collider (CLIC). We give an overview and status of: 1) Drive-beam components: quadrupole magnets and the beam phase feed-forward prototype. 2) Beam instrumentation: stripline and cavity beam position monitors, an electro-optical longitudinal bunch profile monitor, and laserwire and diffraction and transition radiation monitors for transverse beam-size determination. 3) Beam delivery system and machinedetector interface design, including beam feedback/control systems and crab cavity design and control. 4) RF structure design. In each case we report on the status of prototype systems and performance tests with beam at the CTF3, ATF2 and CESRTA test facilities, including plans for future experiments.


A sub-micron resolution, wide-band, stripline bpm system for driving bunch-by-bunch feed-back and feed-forward systems at ATF

IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference (2014) 1358-1360

GB Christian, DR Bett, N Blaskovic Kraljevic, PN Burrows, MR Davis, Y Kim, C Perry

Copyright © 2014 CC-BY-3.0 and by the respective authors. A low-latency, sub-micron resolution stripline beam position monitoring (BPM) system has been developed and tested with beam at the KEK Accelerator Test Facility (ATF2), where it has been used as part of a beam stabilisation system. The fast analogue front-end signal processor is based on a single-stage RF down-mixer and a position resolution below 400 nm has been demonstrated for beam intensities of 1 nC, with single-pass beam. The BPM position data are digitised by fast ADCs on an FPGA-based digital feedback controller, which is used to drive either a pair of kickers local to the BPMs and nominally orthogonal in phase, in closed-loop feedback mode, or a downstream kicker in the ATF2 final focus region, in feedforward mode. The beam jitter is measured downstream of the final focus system with high resolution, low-Q, cavity BPMs, and the relative performance of both systems in stabilising the beam is compared.


Experimental validation of a novel compact focusing scheme for future energy-frontier linear lepton colliders.

Physical review letters 112 (2014) 034802-

GR White, R Ainsworth, T Akagi, J Alabau-Gonzalvo, D Angal-Kalinin, S Araki, A Aryshev, S Bai, P Bambade, DR Bett, G Blair, C Blanch, O Blanco, N Blaskovic-Kraljevic, B Bolzon, S Boogert, PN Burrows, G Christian, L Corner, MR Davis, A Faus-Golfe, M Fukuda, J Gao, H García-Morales, N Geffroy, H Hayano, AY Heo, M Hildreth, Y Honda, JY Huang, WH Hwang, Y Iwashita, S Jang, A Jeremie, Y Kamiya, P Karataev, ES Kim, HS Kim, SH Kim, YI Kim, S Komamiya, K Kubo, T Kume, S Kuroda, B Lam, K Lekomtsev, S Liu, A Lyapin, E Marin, M Masuzawa, D McCormick, T Naito, J Nelson, LJ Nevay, T Okugi, T Omori, M Oroku, H Park, YJ Park, C Perry, J Pfingstner, N Phinney, A Rawankar, Y Renier, J Resta-López, M Ross, T Sanuki, D Schulte, A Seryi, M Shevelev, H Shimizu, J Snuverink, C Spencer, T Suehara, R Sugahara, T Takahashi, R Tanaka, T Tauchi, N Terunuma, R Tomás, J Urakawa, D Wang, M Warden, M Wendt, A Wolski, M Woodley, Y Yamaguchi, T Yamanaka, J Yan, K Yokoya, F Zimmermann, ATF2 Collaboration

A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [P. Raimondi and A. Seryi, Phys. Rev. Lett. 86, 3779 (2001)]. This scheme has many advantageous properties over previously studied focusing schemes, including being significantly shorter for a given energy and having a significantly better energy bandwidth. Experimental results from the ATF2 accelerator at KEK are presented that validate the operating principle of such a scheme by demonstrating the demagnification of a 1.3 GeV electron beam down to below 65 nm in height using an energy-scaled version of the compact focusing optics designed for the ILC collider.


Applications of stripline and cavity beam position monitors in low-latency, high-precision, intra-train feedback systems

IBIC 2013: Proceedings of the 2nd International Beam Instrumentation Conference (2013) 630-633

MR Davis, DR Bett, PN Burrows, N Blaskovic Kraljevic, GB Christian, YI Kim, C Perry

Copyright © 2013 by JACoW. Two low-latency, sub-micron, beam position monitoring (BPM) systems have been developed and tested with beam at the KEK Accelerator Test Facility (ATF2). One system (upstream), based on stripline BPMs, uses fast analogue front-end signal processing and has demonstrated a position resolution as low as 400 nm for beam intensities of 1 nC, with single-pass beam. The other (IP) system, based on low-Q cavity BPMs and utilising custom signal processing electronics designed for low latency, provides a single pass resolution of approximately 100 nm. The BPM position data are digitised by fast ADCs on a custom FPGA-based feedback controller and used in three modes: 1) the upstream BPM data are used to drive a pair of local kickers nominally orthogonal in phase in closed-loop feedback mode; 2) the upstream BPM data are used to drive a downstream kicker in the ATF2 final focus region in feedforward mode; 3) the IP cavity BPM data are used to drive a local downstream kicker in the ATF2 final focus region in closed-loop feedback mode. In each case the beam jitter is measured downstream of the final focus system with the IP cavity BPMs. The relative performance of these systems is compared.


Cavity beam position monitor in multiple bunch operation for the ATF2 interaction point region

IBIC 2013: Proceedings of the 2nd International Beam Instrumentation Conference (2013) 419-422

YI Kim, DR Bett, N Blaskovic Kraljevic, PN Burrows, GB Christian, MR Davis, C Perry, ST Boogert, A Lyapin, Y Honda, T Tauchi, N Terunuma, J Urakawa, J Frisch, D McCormick, J Nelson, GR White

Copyright © 2013 by JACoW. Ultra-high position resolution cavity beam position monitors (BPMs) have been developed to measure the beam position and to be linked to control the beam position stability within a few nanometres in the vertical direction at the focus, Interaction Point (IP), of the Accelerator Test Facility 2 (ATF2). In addition, for feedback applications a lower-Q and hence faster decay time system is desirable. Specialised cavities which is called Interaction Point BPM (IPBPM) has been tested in the ATF2 extraction beam line. Using IPBPMs, a position resolution of less than 5 nm has been measured in single bunch operation. Multibunch operation is also planned at ATF2 for the beam stabilisation. The nominal operation bunch spacing for the International Linear Collider (ILC) is 308 ns so the multibunch operation bunch spacing is ILC like. The IPBPM should be able to measure beam position to nanometre precision in multi-bunch modes. Therefore the position resolution in multi-bunch operation was also measured at ATF2 extraction line. The analysis method of cavity signals, calibration and results of multibunch operation are discussed in this proceeding.


Cavity beam position monitor at the interaction point region of accelerator test facility 2

IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference (2013) 807-809

YI Kim, D Bett, NB Kraljevic, PN Burrows, G Christian, MR Davis, C Perry, ST Boogert, A Lyapin, Y Honda, T Tauchi, N Terunuma, J Urakawa, J Frisch, D McCormick, J Nelson, GR White

Nanometre resolution cavity beam position monitors (BPMs) have been developed to measure the beam position and to be linked to control the beam position stability within a few nanometres in the vertical direction at the focus, or Interaction Point (IP), of the Accelerator Test Facility 2 (ATF2). In addition, for feedback applications a lower-Q and hence faster decay time system is desirable. Two cavity so-called IP BPMs have been installed inside the IP chamber at the ATF2 focus area. To measure the resolution of IPBPMs two additional C-band cavity BPMs have been installed one upstream and one downstream of the IP. One cavity BPM has been installed at an upstream vertical image point of the IP. The performance of the BPMs is discussed and the correlation between the IP and image point positions is presented along with a discussion of using these BPMs for position stabilisation at the IP. Copyright © 2013 by JACoW.


Development of a high-resolution, broad-band, stripline beam position monitoring system

IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference (2013) 804-806

DR Bett, NB Kraljevic, PN Burrows, GB Christian, MR Davis, YI Kim, C Perry, R Apsimon, B Constance, JR Lopez

A low-latency, sub-micron resolution stripline beam position monitoring system has been developed and tested with beam at the KEK Accelerator Test Facility, where it has been used as part of a feedback system for beam stabilisation. The fast analogue front-end signal processor is based on a single-stage down-mixer and is combined with an FPGA-based system for digitisation and feedback control. A resolution as low as 400 nm has been demonstrated for beam intensities of ∼1 nC, with singlepass beam. The latest results of recent modifications to balance the input path lengths to the processor will be discussed. These modifications compensate for the inherent phase sensitivity of the processors, and hence improve the intrinsic resolution, without the need for offline correction. Modifications to the FPGA firmware will also be described, to allow for flexible operation with variable system-synchronous data acquisition at up to 400 MHz, with up to nine data channels of 13-bit width, and a nominal record length of 1 kS/channel/pulse (extensible to a total record length of 120 kS per pulse, for example, for use with long bunch trains or wide-band multi-turn measurements in storage rings). Copyright © 2013 by JACoW.


Latest performance results from the font 5 intra train beam position feedback system at ATF

IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference (2013) 3049-3051

PN Burrows, DR Bett, NB Kraljevic, GB Christian, MR Davis, YI Kim, C Perry, RJ Apsimon, B Constance, A Gerbershagen

A prototype ultra-fast beam-based feedback system for deployment in single-pass beamlines, such as a future lepton collider (ILC or CLIC) or a free-electron laser, has been fabricated and is being tested in the extraction and final focus lines of the Accelerator Test Facility (ATF) at KEK. FONT5 is an intra-train feedback system for stabilising the beam orbit via different methods: A position and angle feedback correction in the extraction line or a vertical feedforward correction applied at the interaction point (IP). Two systems comprise three stripline beam position monitors (BPMs) and two stripline kickers in the extraction line, two cavity BPMs and a stripline kicker at the IP, a custom FPGA-based digital processing board, custom kicker-drive amplifiers and low-latency analogue front-end BPM processors. Latest results from the experiment are presented. These include beam position correction in the extraction line, as well as preliminary results of beam correction at the IP. Copyright © 2013 by JACoW- cc Creative Commons Attribution 3.0 (CC-BY-3.0).


A low-latency sub-micron resolution stripline beam position monitoring system for single-pass beamlines

IPAC 2012 - International Particle Accelerator Conference 2012 (2012) 933-935

PN Burrows, DR Bett, N Blaskovic Kraljevic, GB Christian, MR Davis, C Perry, RJ Apsimon, B Constance, A Gerbershagen, J Resta Ĺopez

A low-latency, sub-micron resolution stripline beam position monitoring system has been developed for use in single-pass beamlines. The fast analogue front-end signal processor is based on a single-stage RF down-mixer and is combined with an FPGA-based system for digitisation and further signal processing. The system has been deployed and tested with beam at the Accelerator Test Facility at KEK. Performance results are presented on the calibration, resolution and stability of the system. A detailed simulation has been developed that is able to account for the measured performance. Copyright © 2012 by IEEE.


Latest performance results from the font5 intra-train beam position and angle feedbacksystem at ATF2

IPAC 2012 - International Particle Accelerator Conference 2012 (2012) 2864-2866

DR Bett, N Blaskovic Kraljevic, PN Burrows, GB Christian, MR Davis, C Perry, R Apsimon, B Constance, A Gerbershagen, J Resta Lopez

A prototype Interaction Point beam-based feedback system for future electron-positroncolliders, such as the International Linear Collider, has been designed and tested on theextraction line of the KEK Accelerator Test Facility (ATF). The FONT5 intra-train feedbacksystem aims to stabilize the beam orbit by correcting both the position and angle jitter inthe vertical plane on bunch-tobunch time scales, providing micron-level stability at theentrance to the ATF2 final-focus system. The system comprises three stripline beam positionmonitors (BPMs) and two stripline kickers, custom low-latency analogue front-end BPMprocessors, a custom FPGA-based digital processing board with fast ADCs, and customkickerdrive amplifiers. The latest results from beam tests at ATF2 will be presented,including the system latency and correction performance. Copyright © 2012 by IEEE.


Study of transverse pulse-to-pulse orbit jitter at the kek accelerator test facility 2 (atf2)

IPAC 2012 - International Particle Accelerator Conference 2012 (2012) 936-938

J Resta-Lopez, J Alabau-Gonzalvo, DR Bett, PN Burrows, GB Christian, MR Davis, C Perry, R Apsimon, B Constance, A Gerbershagen

For future linear colliders the precise control and mitigation of pulse-to-pulse orbit jitter will be very important to achieve the required luminosity. Diagnostic techniques for the orbit jitter measurement and correction for multibunch operation are being addressed at the KEK Accelerator Test Facility 2 (ATF2). In this paper we present recent studies on the vertical jitter propagation through the ATF2 extraction line and final focus system. For these studies the vertical pulse-to-pulse position and angle jitter have been measured using the available stripline beam position monitors in the beamline. The cases with and without intra-train orbit feedback correction in the ATF2 extraction line are compared. Copyright © 2012 by IEEE.


Development of a turn-by-turn beam position monitoring system for multiple bunch operation of the atf damping ring

IPAC 2012 - International Particle Accelerator Conference 2012 (2012) 930-932

PN Burrows, DR Bett, N Blaskovic Kraljevic, GB Christian, MR Davis, C Perry, RJ Apsimon, B Constance, A Gerbershagen, J Resta-Ĺopez

An FPGA-based monitoring system has been developed to study multi-bunch beam instabilities in the damping ring (DR) of the KEK Accelerator Test Facility (ATF). The system utilises a stripline beam position monitor (BPM) and single-stage down-mixing BPM processor. The system is designed to record the horizontal and/or vertical positions of up to three bunches in the DR with c. 150ns bunch spacing, or the head bunch of up to three trains in a multi-bunch mode with a bunch spacing of 5.6 ns. The FPGA firmware and data acquisition software allow the recording of turnby- turn data. An overview of the system and performance results will be presented. Copyright © 2012 by IEEE.

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