Diagnostics for Hadron Accelerators

Paper Title Page
RPAT001 Experimental Results of a Non-Destructive Emittance Measurement Device for H- Beams 782
  • C. Gabor, H. Klein, O. Meusel, U. Ratzinger
    IAP, Frankfurt-am-Main
  • J. Pozimski
    Imperial College of Science and Technology, Department of Physics, London
  For the diagnostic of high power ion beams, non-destructive measurement devices should not only provide minimum influence on the beam itself, but also avoid various problems that occur when the high power density of the beam penetrates surfaces like slit- or pinhole plates. On the other hand, measurements of resolution should be comperable with destructive methods. Beams of negative ions offer the use of a non-destructive Emittance Measurement Instrument (EMI) based on the principle of photo detachment. Interaction of laser photons with the negative ions causes electron detachment. Due to moving the postion of the well collimated laser beam acros the ion beam the produced neutral atoms are well suited to detect the transverse beam emittance like a classical slit-grid device. After separation in a magnetic dipole, the neutrals can be viewed on a scintillator screen with a CCD camera. To investigate the use of such a photo detachment EMI and to study the transport of negative ions an experiment consisting of H minus ion source, electrostatic LEBT and EMI was constructed. The paper will present the setup of the experimental hardware and first results of measurements.  
RPAT002 Production of Inorganic Thin Scintillating Films for Ion Beam Monitoring Devices 808
  • M. Re, G.A.P. Cirrone, L. Cosentino, G. Cuttone, P. Finocchiaro, P.A. Lojacono
    INFN/LNS, Catania
  • A. Hermanne, H. Thienpont, J. Van Erps, M. Vervaeke, B. Volckaerts, P. Vynck
    VUB, Brussels
  • Y.J. Ma
    CIAE, Beijing
  In this work we present the development of beam monitoring devices consisting of thin CsI(Tl) films deposited on Aluminium support layers. The light emitted by the scintillating layer during the beam irradiation is measured by a CCD-camera. In a first prototype a thin Aluminium support layer of 6 micron allows the ion beam to easily pass through without significant energy loss and scattering effects. Therefore it turns out to be a non-destructive monitoring device to characterize on-line beam shape and beam position without interfering with the rest of the irradiation process. A second device consists of an Aluminium support layer which is thick enough to completely stop the impinging ions allowing to monitor at the same time the beam profile and the beam current intensity. Some samples have been coated by a 100 Å protective layer to prevent the film damage by atmosphere exposition. In this contribution we present our experimental results obtained by irradiating the samples with proton beams at 8.3 and 62 MeV. We also propose some innovative applications of these beam monitoring devices in different nuclear sectors such as cancer proton therapy and high intensity beam accelerators.  
RPAT005 Beam Diagnostics for the J-PARC Main Ring Synchrotron 958
  • T. Toyama, D.A. Arakawa, Y. Hashimoto, S. Lee, T. Miura, S. Muto
    KEK, Ibaraki
  • N. Hayashi, J. Kishiro, R. Toyokawa
    JAERI/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  Beam diagnostics: beam intensity monitors (DCCT, SCT, FCT, WCM), beam position monitors (ESM), beam loss monitors (proportional chamber, air ion chamber), beam profile monitors (secondary electron emission, gas-sheet) have been designed, tested, and will be installed for the Main Ring synchrotron of J-PARC (Japan Proton Accelerator Research Complex). This paper describes the basic design principle and specification of each monitor, with a stress on how to cope with high power beam (average circulation current of ~12 A) and low beam loss operation (less than 1 W/m except a collimator region). Some results of preliminary performance test using present beams and a radiation source will be reported.  
RPAT006 Design and Initial Tests of a Gas Scattering Energy Monitor in the PEFP RFQ and DTL 997
  • S.-H. Han, Y.-S. Cho
    KAERI, Daejon
  Funding: This work is supported by the 21C Frontier R&D program in the Ministry of Science and Technology of the Korean government.

We have developed a gas scattering energy monitor to measure the energy spectrum of the proton beam at the end of 3MeV RFQ and 20MeV DTL for the low energy part of the PEFP(Proton Engineering Frontier Project). The energy monitor is comprised of a Xe scattering chamber, two collimators to reduce the beam intensity, and a surface barrier detector for measuring the proton energy. In order to measure the beam current simultaneously, a faraday cup is incorporated into the energy monitor. The calculated flux attenuation through the 0.2 mm diameter collimator is 3·10-4 and the energy loss is 28 keV. We report on design details and multiple gas scattering of proton beams in Xe gas by using a SRIM code.

RPAT007 Status of Beam Diagnostic Systems for the PEFP 1090
  • J.H. Park, J.Y. Huang, W.H. Hwang, Y.W. Parc, S.J. Park
    PAL, Pohang, Kyungbuk
  • Y.-S. Cho, B.H. Choi, S.-H. Han
    KAERI, Daejon
  Funding: Supported by the PEFP (Proton Engineering Frontier Project).

A proton linear accelerator is currently the construction at the KAERI (Korea Atomic Research Institute) to the PEFP (Proton Engineering Frontier Project) in Korea. We are accomplished the technique development of beam diagnostic system to be currently the construction. We treat beam diagnostics for the high power proton linear accelerator. Prototype beam position & phase monitor (BPPM) electronics was made and tested successfully in one of the beam diagnostic systems. The beam position monitor pickup electrode is a capacitive type (electrostatic type) which has a button form. Button form electrode, in common use around electron synchrotrons and storage rings, are a variant of the electrode with small button form (e.g., sub mm diameter). However, we are designed button form electrode to measure beam position of proton beam. The BCM (Beam Current Monitor) is developed Tuned CT (Current Transformer) for collaborate with Bergoz Instruments. This paper describes the status of beam diagnostic systems for the PEFP.

RPAT008 Prototype Digital Beam Position and Phase Monitor for the 100-MeV Proton Linac of PEFP 1120
  • I.H. Yu, D.T. Kim, S.-C. Kim, I.-S. Park, S.J. Park
    PAL, Pohang, Kyungbuk
  • Y.-S. Cho
    KAERI, Daejon
  Funding: Work supported by the PEFP (Proton Engineering Frontier Project), Korea.

The PEFP (Proton Engineering Frontier Project) at the KAERI (Korea Atomic Energy Research Institute) is building a high-power proton linear accelerator aiming to generate 100-MeV proton beams with 20-mA peak current (pulse width and max. repetition rate of 1 ms and 120 Hz respectively). We are developing a prototype digital BPPM (Beam Position and Phase Monitor) for the PEFP linac utilizing the digital technology with field programmable gate array (FPGA). The RF input signals are down converted to 10 MHz and sampled at 40 MHz with 14-bit ADC to produce I and Q data streams. The system is designed to provide a position and phase resolution of 0.1% and 0.1? RMS respectively. The fast digital processing is networked to the EPICS-based control system with an embedded processor (Blackfin). In this paper, the detailed description of the prototype digital beam position and phase monitor will be described with the performance test results.

RPAT009 FPGA-Based Instrumentation for the Fermilab Antiproton Source 1159
  • B. Ashmanskas, S. U. Hansen, T. Kiper, D.W. Peterson
    Fermilab, Batavia, Illinois
  We have designed and built low-cost, low-power, ethernet-based circuit boards to apply DSP techniques to several instrumentation upgrades in the Fermilab Antiproton Source. Commodity integrated circuits such as direct digital synthesizers, D/A and A/D converters, and quadrature demodulators enable digital manipulation of RF waveforms. A low cost FPGA implements a variety of signal processing algorithms in a manner that is easily adapted to new applications. An embedded microcontroller provides FPGA configuration, control of data acquisition, and command-line interface. A small commercial daughter board provides an ethernet-based TCP/IP interface between the microcontroller and the Fermilab accelerator control network. The board is packaged as a standard NIM module. Applications include Low Level RF control for the Debuncher, readout of transfer-line Beam Position Monitors, and narrow-band spectral analysis of diagnostic signals from Schottky pickups.  
RPAT011 Digital Signal Processing the Tevatron BPM Signals 1242
  • G.I. Cancelo, E. James, S.A. Wolbers
    Fermilab, Batavia, Illinois
  Funding: Fermilab

The Beam Position Monitor (BPM) readout system at Fermilab’s Tevatron has been updated and is currently being commissioned. The new BPMs use new analog and digital hardware to achieve better beam position measurement resolution. The new system reads signals from both ends of the existing directional stripline pickups to provide simultaneous proton and antiproton position measurements. The signals provided by the two ends of the BPM pickups processed by analog band-pass filters and sampled by 14-bit ADCs at 74.3MHz. A crucial part of this work has been the design of digital filters that process the signal. This paper describes the digital processing and estimation techniques used to optimize the beam position measurement. The BPM electronics must operate in narrow-band and wide-band modes to enable measurements of closed-orbit and turn-by-turn positions. The filtering and timing conditions of the signals are tuned accordingly for the operational modes. The analysis and the optimized result for each mode is presented.

RPAT012 A Hardware Transverse Beam Frequency Response Simulator 1269
  • J. Ning, C.-Y. Tan
    Fermilab, Batavia, Illinois
  Funding: Fermi National Accelerator Lab.

We build an electronical instrument to get the frequency response close to the pattern of transverse beam frequency response. The method is to apply 1)a time delay circuit with ADC, FIFO RAM and DAC; 2)a phase shift circuit which is an all pass filter with adjustable phase shift in the frequency range of 25kHz to 30kHz; in a feedback loop of 3)a commutating filter which is a high Q band pass filter. We can dynamically adjust the center frequency, the side band distance during the testing. With this instrument, some beam instruments can be tested without using the real beam.

RPAT013 Signal Processing for Longitudinal Parameters of the Tevatron Beam 1362
  • S. Pordes, J.L. Crisp, B.J. Fellenz, R.H. Flora, A. Para, A.V. Tollestrup
    Fermilab, Batavia, Illinois
  Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy.

The time profiles of the bunches in the Tevatron are obtained by sampling the output of a resistive wall current monitor with a 5GS/s, 2GHz bandwidth, Lecroy 6200 oscilloscope. The techniques for removing the effect of cable dispersion and for extending the dynamic range of the data by splitting the signal and using two input channels at different gains are described. The algorithms for taking these data in the time domain and deriving the momentum spread and longitudinal emittance are also given.

RPAT015 First Results of a Digital Beam Phase Monitor at the Tevatron 1428
  • J.-P. Carneiro, S. U. Hansen, A. Ibrahim, V.D. Shiltsev, J. Steimel, R.C. Webber
    Fermilab, Batavia, Illinois
  A digital Beam Phase Monitor has been installed on the Tevatron ring. This device will be mainly use to diagnose the energy oscillations of each of the 36 × 36 protons and antiprotons bunches as well as to study the transient beam loading. The first results obtained from the Beam Phase Monitor will be presented on the paper.  
RPAT017 Using Time Separation of Signals to Obtain Independent Proton and Antiproton Beam Position Measurements Around the Tevatron 1557
  • R.C. Webber
    Fermilab, Batavia, Illinois
  Funding: Fermilab is operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy.

Independent position measurement of the counter-circulating proton and antiproton beams in the Tevatron presents a challenge to upgrading the Tevatron Beam Position Monitor (BPM) system. The inherent directionality of the Tevatron BPM pickup design provides 26dB isolation between signals from the two beams. At the present typical 10:1 proton-to-antiproton bunch intensity ratio, this isolation alone is insufficient to support millimeter accuracy antiproton beam position measurements due to interfering proton signals. An accurate and manageable solution to the interfering signal problem is required for antiproton measurements now and, as machine improvements lead to increased antiproton intensity, will facilitate future elimination of antiproton bias on proton beam position measurements. This paper discusses the possibilities and complications of using time separation of the two beam signals at the numerous Tevatron BPM locations and given the dynamic longitudinal conditions of Tevatron operation. Results of measurements results using one such method are presented.

RPAT018 Simultaneous Position Measurements of Protons and Anti-Protons in the Tevatron 1613
  • R.K. Kutschke, J. Steimel, R.C. Webber, S.A. Wolbers
    Fermilab, Batavia, Illinois
  Fermilab has embarked upon a program to upgrade the electronics of the Beam Position Monitor (BPM) system that measures the transverse position of the beams inside the Tevatron collider. The new system improves on the current system in precision, accuracy and reliability. A new feature in the upgraded system is the ability, when both protons and anti-protons are present in the Tevatron, make simultaneous measurements of the closed orbit position of both beam species. The method chosen for achieving the simultaneous measurement is an algorithm that deconvolutes the imperfect directionality of the BPM pickups from the raw measurements. This paper will discuss the algorithm, the calibration of the parameters used by the algorithm and the robustness of the algorithm. It will also present results from the upgraded system which demonstrate that the system meets the requirements set out at the start of the upgrade project.  
RPAT019 Use of a Reconfigurable VME Module To Measure Beam Energy at the Los Alamos Proton Storage Ring 1658
  • R. Merl, T. Spickermann
    LANL, Los Alamos, New Mexico
  Funding: U.S. Department of Energy.

Custom instrumentation has been developed at the Los Alamos Neutron Science Center to measure the Proton Storage Ring (PSR) beam energy. The PSR accumulates up to 4x1013 protons from the linear accelerator for delivery to a spallation neutron source. The energy of the beam injected into the PSR must be adjusted so that the revolution frequency matches the ring buncher frequency, otherwise a large momentum spread will cause increased losses in high-dispersion areas. Errors in injected beam energy appear as deviations from the ideal revolution frequency. A low-cost, custom, reconfigurable VME module has been adapted to calculate the PSR revolution frequency in real-time. The module connects directly to an analog wall current monitor output and uses analog signal conditioning electronics, an analog to digital converter, field programmable gate arrays, and an embedded floating-point digital signal processor to calculate the revolution frequency. This is an improvement over the previously used method of manually measuring the frequency with an oscilloscope. Accelerator physicists can now simply observe the PSR frequency, which is dependent on beam energy, on a control room display.


RPAT022 Optical Faraday Cup for Heavy Ion Beams 1805
  • F.M. Bieniosek, S. Eylon, P.K. Roy, S. Yu
    LBNL, Berkeley, California
  Funding: Work performed under the auspices of the U.S. Department of Energy by the university of California, Lawrence Berkeley National Laboratory under Contract No. DE-AC03-76F00098.

We have been using alumina scintillators for imaging beams in heavy-ion beam fusion experiments in 2 to 4 transverse dimensions.* The scintillator has limitations on lifetime, linearity, and time response. As a possible replacement for the scintillator, we are studying the technique of imaging the beam on a gas cloud. A gas cloud for imaging the beam may be created on a solid hole plate placed in the path of the beam, or by a localized gas puff. It is possible to image the beam using certain fast-quenching optical spectral lines that closely follow beam current density and are independent of gas density. We describe this technique and show experimental data using a nitrogen line at 394.1 nm. This approach has promise to be a new fast beam current diagnostic on a nanosecond time scale.

*FM Bieniosek, L Prost, W Ghiorso, Beam imaging diagnostics for heavy ion beam fusion experiments, Paper WPPB050, PAC 2003.

RPAT027 Tomographic Measurement of Longitudinal Emittance Growth Due to Stripping Foils 2000
  • C. Montag, L. Ahrens, P. Thieberger
    BNL, Upton, Long Island, New York
  Funding: Work performed under the auspices of the US Department of Energy.

During beam acceleration at the Brookhaven accelerator complex, heavy ions are stripped off their electrons in several steps. Depending on the properties of the stripping foils, this process results in an increased energy spread and therefore longitudinal emittance growth. A tomographic phase space reconstruction technique has been applied to quantify the associated emittance growth for different stripping foil materials.

RPAT028 RHIC BPM System Modifications and Performance 2021
  • T. Satogata, R. Calaga, P. Cameron, P. Cerniglia, J. Cupolo, A.J. Curcio, W.C. Dawson, C. Degen, J. Gullotta, J. Mead, R.J. Michnoff, T. Russo, R. Sikora
    BNL, Upton, Long Island, New York
  Funding: Work performed under the auspices of the U.S. Department of Energy.

The RHIC beam position monitor (BPM) system provides independent average orbit and turn-by-turn (TBT) position measurements. In each ring, there are 162 measurement locations per plane (horizontal and vertical) for a total of 648 BPM planes in the RHIC machine. During 2003 and 2004 shutdowns, BPM processing electronics were moved from the RHIC tunnel to controls alcoves to reduce radiation impact, and the analog signal paths of several dozen modules were modified to eliminate gain-switching relays and improve signal stability. This paper presents results of improved system performance, including stability for interaction region and sextupole beam-based alignment efforts. We also summarize performance of improved million-turn TBT acquisition channels for nonlinear dynamics and echo studies.

RPAT031 Beam Profile Measurement with Flying Wires at the Fermilab Recycler Ring 2182
  • M. Hu, R. H. Carcagno, J. Krider, E. Lorman, A. Marchionni, Y.M.P. Pischalnikov, S. Pordes, D. Slimmer, J. Wilson, J.R. Zagel
    Fermilab, Batavia, Illinois
  The Fermilab Recycler Ring is a high vacuum fixed energy antiproton storage ring with stochastic and electron cooling systems. Flying wires were installed at the Fermilab Recycler Ring for transverse beam profile measurement. The following note describes the system configuration, calibration and resolution of the flying wire system, as well as analysis of the transverse beam profile in the presence of both cooling systems.  
RPAT032 An Ionization Profile Monitor for the Tevatron 2227
  • A. Jansson, M. Bowden, K. Bowie, A. Bross, R. Dysert, T. Fitzpatrick, R. Kwarciany, C. Lundberg, H. Nguyen, C.H. Rivetta, D. Slimmer, L. Valerio, J.R. Zagel
    Fermilab, Batavia, Illinois
  Funding: Work supported by the U.S. Department of Energy.

Primarily to study emittance blowup during injection and ramping, an ionization profile monitor has been developed for the Tevatron. It is based on a prototype installed in the Main Injector, although with extensive modifications. In particular, the electromagnetic shielding has been improved, the signal path has been cleaned up, and provisions have been made for an internal electron source. Due to the good Tevatron vacuum, a local pressure bump is introduced to increase the primary signal, which is then amplified by a microchannel plate and detected on anode strips. For the DAQ, a custom ASIC developed for the CMS experiment is used. It is a combined charge integrator and digitizer, with a sensitivity of a few fC, and a time-resolution that allows single bunch measurement. Digitization is done in the tunnel to reduce noise. Preparations for detector installation were made during the long 2004 shutdown, with the installation of magnets, vacuum chambers, vacuum pumps and cabling. The actual detector will be installed sometime during the spring fo 2005. This paper describes the design of the detector and associated electronics and presents various bench test results.

RPAT033 Beta Function Measurement in the Tevatron Using Quadrupole Gradient Modulation 2272
  • A. Jansson, P. Lebrun, J.T. Volk
    Fermilab, Batavia, Illinois
  Funding: Work supported by the U.S. Department of Energy.

Early in Run2, there was an effort to compare the different emittance measurements in the Tevatron (flying wires and synchtotron light) and understand the origin of the observed differences. To measure the beta function at a few key locations near the instruments, air-core quadrupoles were installed. By modulating the gradient of these magents and measuring the effect on the tune, the lattice parameters can be extracted. Initially, the results seem to disagree with with other methods. At the time, the lattice was strongly coupled due to a skew component in the main dipoles, caused by sagging of the cryostat. After a large fraction of the superconducting magnets were shimmed to remove a strong skew quadrupole component, the results now agree with expectations, confirming that the beta function is not the major error source of discrepancy in the emittance measurement.

RPAT035 Development of an Optical Transition Radiation Detector for Profile Monitoring of Antiproton and Proton Beams at FNAL 2381
  • V.E. Scarpine, C.W. Lindenmeyer, G. R. Tassotto
    Fermilab, Batavia, Illinois
  • A.H. Lumpkin
    ANL, Argonne, Illinois
  Funding: Work Supported by the U.S. Department of Energy under Contract No. DE-AC02-CH03000 and by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

Optical transition radiation (OTR) detectors are being developed at Fermi National Acceleratory Laboratory (FNAL) as part of the collider Run II upgrade program and as part of the NuMI primary beamline. These detectors are designed to measure 150 GeV antiprotons as well as 120 GeV proton beams over a large range of intensities. Design and development of an OTR detector capable of measuring beam in both directions down to beam intensities of ~5·109 particles for nominal beam sizes is presented. Applications of these OTR detectors as an on-line emittance monitor for both antiproton transfers and reverse-injected protons, as a Tevatron injection profile monitor, and as a high-intensity beam profile monitor for NuMI are discussed. In addition, different types of OTR foils are being evaluated for operation over the intensity range of ~5·109 to over 1·1013 particles per pulse and these are described.

RPAT036 Measurement of the Intensity of the Beam in the Abort Gap at the Tevatron Utilizing Synchrotron Light 2440
  • R. Thurman-Keup, E. Lorman, T. Meyer, S. Pordes
    Fermilab, Batavia, Illinois
  • S. De Santis
    LBNL, Berkeley, California
  Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the U.S. Department of Energy.

The beam bunches in the Tevatron are arranged to provide gaps in time for the abort kickers to ramp to full field. The presence of even a small fraction (few 10-4)of the beam in the abort gaps can induce quenches of the superconducting magnets and inflict severe radiation damage on the silicon detectors of the experiments. Techniques for calibrating and measuring the intensity of the beam in the abort gap using synchrotron light and a gated photomultiplier tube are described. Measurements of the evolution and longitudinal profile of the beam in the abort gap are presented.

RPAT038 Diagnostic for Electron Clouds Trapped in Quadrupoles 2547
  • R.J. Macek, A. A. Browman
    TechSource, Santa Fe, New Mexico
  Funding: Work supported by a DOE SBIR Phase I grant DE-FG02-04ER84105.

Simulations have indicated that electron clouds generated by beam-induced multipactor can be trapped in the mirror-like fields of magnetic quadrupoles and thereby contribute significantly to the electron cloud buildup in high intensity accelerators and storage rings. This could be the most important source of electrons driving the two-stream (e-p) instability at the Los Alamos PSR and may also play a significant role in electron cloud effects at some of the new high intensity accelerator projects. We will describe the physics design and optimization of an electron-sweeping detector designed to measure the trapped electrons at various times after the beam pulse has passed. The instrument can also serve as an electro-magnetically shielded detector providing a signal obtained from electrons striking the wall during the passage of beam bunches.

RPAT039 Feasibility Study of Using an Electron Beam for Profile Measurements in the SNS Accumulator Ring 2586
  • A.V. Aleksandrov, S. Assadi, S.M. Cousineau, V.V. Danilov, S. Henderson, M.A. Plum
    ORNL, Oak Ridge, Tennessee
  • P.V. Logatchev, A.A. Starostenko
    BINP SB RAS, Novosibirsk
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.

The design goal for the SNS ring is to accumulate 2·1014 protons per 1ms pulse at a 60Hz repetition rate. Achieving the design beam intensity with acceptable losses is a challenging task, which could be tackled more easily if reliable measurements of the beam profile in the ring are available. The high power density of the beam precludes the use of conventional wire scanners or harps and therefore non-interceptive types of profiles measurements are required. The electron beam probe method was suggested for measuring profiles in high power beams. In this method, deflection of a low energy electron beam by the collective field of the high intensity beam is measured. The charge density in the high intensity beam can be restored under certain conditions or estimated by various mathematical techniques. We studied the feasibility of using the electron beam probe for the SNS accumulator ring using computer simulations of the diagnostic setup. A realistic electron gun model and realistic proton beam distributions were used in the simulations. Several profile calculation techniques were explored and the results are reported in this paper.

RPAT040 Matching BPM Stripline Electrodes to Cables and Electronics 2607
  • C. Deibele
    ORNL, Oak Ridge, Tennessee
  • S.S. Kurennoy
    LANL, Los Alamos, New Mexico
  Funding: This work was supported by SNS through UT-Batelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. The SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge.

The Spallation Neutron Source (SNS) is an accelerator-based neutron source being built at Oak Ridge National Laboratory. The 805-MHz coupled-cavity linac (CCL) accelerates an H- beam from 86 to 186 MeV, while the 805 MHz superconducting-cavity linac (SCL) accelerates the beam to its final energy of 1 GeV. The SNS beam position monitors (BPMs) which are used to measure both position and phase of the beam relative to the master oscillator, have the dual-planed design with four one-end-shorted stripline electrodes. We argue that the BPMs are optimally broadband matched to the cabling and electronics when the geometrical mean of the sum-mode and quadrupole-mode impedances is equal to the external-line impedance, 50 Ohms. The analytical results, MAFIA and HFSS simulations, wire measurements, and beam measurements that support this statement are presented.

RPAT042 Emittance Scanner Optimization for Low Energy Ion Beams 2705
  • M.P. Stockli, R.F. Welton
    ORNL, Oak Ridge, Tennessee
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.

Ion beam emittances are normally measured as two-dimensional distributions of the beam current fraction within a window dx centered at position coordinate x and a window dx’ centered at trajectory angle x’. Unthresholded rms emittances evaluated from experimental data are very sensitive to noise, bias, and other undesired signals. Undesired signals occur when particles from outside the measured window dx*dx’ contribute to the signal from the particles within the measured window. Increasing the window size increases the desired signal while most undesired contributions remain unchanged. However, the decreasing resolution causes an error in the emittance results, especially in the rms emittance. Using theoretical distributions we will present the tradeoff between resolution and accuracy.

RPAT043 Developments of the Calibration Tools for Beam Position Monitor at J-PARC Linac 2777
  • S. Sato, H. Akikawa, T. Tomisawa, A. Ueno
    JAERI/LINAC, Ibaraki-ken
  • Z. Igarashi, M. Ikegami, N. Kamikubota, S. Lee, T. Toyama
    KEK, Ibaraki
  In the J-PARC LINAC, there are mainly two requirements for the beam based calibration of beam position monitors (BPMs). One is that BPMs need to be calibrated with the accuracy of about a hundred micro-meters to minimize beam loss for the world highest class of proton intensity. The other is that about a hundred of BPMs need to be calibrated consistently. To achieve these requirements, the calibration tool are being developed with experiences on real beam in a MEBT line set for the DTL commissioning. Tools for simulating the beam trajectory using transport matrix (e.g. T3D) are being developed as well. The calibrated beam positions measured by BPMs are used in the simulation for tuning the beam. Implementation of the calibration tools on the same platform (e.g. SAD) with the simulation tools is important for higher usability during commissioning of whole J-PARC. In this paper, details of these developments around BPMs are to be reported.  
RPAT044 Segmented Foil SEM Grids at Fermilab 2821
  • S.E. Kopp, D. Indurthy, Z. Pavlovich, M. Proga, R.M. Zwaska
    The University of Texas at Austin, Austin, Texas
  • B.B. Baller, S.C. Childress, R. Ford, D. Harris, C.L.K. Kendziora, C.D. Moore, G. R. Tassotto
    Fermilab, Batavia, Illinois
  Segmented Secondary Emission Monitors (SEM's) will be used to monitor the extracted 120 GeV proton beam for the NuMI facility at Fermilab. The SEM's are constructed from 5 micrometer thick Ti foils. The chambers have 10 cm beam aperture, and the foils are designed to result in 4·10-6 fractional beam loss when inserted in the beam. The foil strips have dynamic tensioning to withstand the heating from the 400kW proton beam. Results from prototype beam tests as well as from commissioning in the NuMI line will be presented.  
RPAT045 Beam Phase Detection for Proton Therapy Accelerators
  • B. A. Aminov, M. G. Getta, S. K. Kolesov, N. Pupeter
    CRE, Wuppertal
  • A. Geisler, T. Stephani, J. H. Timmer
    ACCEL, Bergisch Gladbach
  The industrial application of proton cyclotrons for medical applications has become one of the important contributions of accelerator physics during the last years. This paper describes an advanced vector demodulating technique used for non-destructive measurements of beam intensity and beam phase over 360°. A computer controlled I/Q-based phase detector with a very large dynamic range of 70 dB permits the monitoring of beam intensity, phase and eventually energy for wide range of beam currents down to –130 dBm. In order to avoid interference from the fundamental cyclotron frequency the phase detection is performed at the second harmonic frequency. A digital low pass filter with adjustable bandwidth and steepness is implemented to improve accuracy. With a sensitivity of the capacitive pickup in the beam line of 30 nV per nA of proton beam current at 250 MeV, accurate phase and intensity measurements can be performed with beam currents down to 3.3 nA.