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beam-losses

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MOP097 Design of a High Energy Beam Stop for Spiral2 linac, target, vacuum, neutron 283
 
  • E. Schibler, J.-C. Ianigro
    IN2P3 IPNL, Villeurbanne
  • J. Morales, N. Redon
    UCBL, Villeurbanne
  • L. Perrot
    IPN, Orsay
 
 

The driver accelerator of the Spiral2 facility will deliver deuteron (40MeV) and proton (33MeV) beams with current up to 5mA and heavy ion (14.5MeV/n) beams up to 1mA. At the very end of the LINAC, the main Beam Stop will have to withstand a peak power of 200kW for deuterons, with an associated power density from 120W/mm2 to more than 700W/mm2. These challenging specifications impose the design of a new high efficiency Beam Stop that has been nicknamed SAFARI (French acronym of Optimized Beam Stop Device for High Intensity Beams). From the beam characteristics and activation constraints, we proposed and developed a complete design. We will present this original design and the different studies and optimizations which have been done: The Beam Stop shape marries to the beam characteristics in order to smooth for the best power density and improve thermo-mechanical behaviour under nominal and critical beams. Cooling system is directly machined from Beam Stop blocks. Optimization by various fluid studies and calculations led us to a new high efficiency counter-current water cooling system. We then compare calculated behaviour with first results obtained on our recent functional mock-up

 
MOP099 Status of the Design of 650 MHz Elliptical Cavities for Project X cavity, linac, proton, coupling 289
 
  • S. Barbanotti, M.H. Foley, I.G. Gonin, J. Grimm, T.N. Khabiboulline, L. Ristori, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia
 
 

Project X is a proposed high-intensity proton accelerator complex that could provide beam to create a high-intensity neutrino beam, feed protons to kaon- and muon-based precision experiments, and for other applications still under investigation. The present configuration of the proton accelerator foresees a section with 650 MHz beta = 0.6 and beta = 0.9 elliptical cavities. Prototypes of single-cell 650 MHz cavities and five-cell beta = 0.9 650 MHz cavities are being designed and fabricated at Fermilab in the R&D process for Project X. This paper summarizes the design status of the beta = 0.6 and beta = 0.9 single-cell prototype cavities, and also addresses the design effort focused on the five-cell beta = 0.9 cavities.

 
MOP108 Planned Machine Protection System for the Facility for Rare Isotope Beams at Michigan State University controls, linac, diagnostics, monitoring 313
 
  • S. Assadi, W. Hartung, M.J. Johnson, T.L. Mann, E. Pozdeyev, E. Tanke, X. Wu, R.C. York, Q. Zhao
    FRIB, East Lansing, Michigan
  • M. Doleans, F. Marti
    NSCL, East Lansing, Michigan
 
 

The Facility for Rare Isotope Beams (FRIB) at Michigan State University will utilize a 400 kW, heavy-ion linear accelerator to produce rare isotopes in support of a rich program of fundamental research. In the event of operating failures, it is extremely important to shut off the beam in a prompt manner to control the beam losses that may damage the accelerator components such as superconducting cavities. FRIB has adapted the residual beam loss activation limit at 30 cm to be equivalent to 1W/m of operating beam losses. We are designing FRIB MPS to be flexible but redundant in safety to accommodate both commissioning and operations. It is also dependent upon the operational mode of the accelerator and the beam dump in use. The operational mode is distributed via a finite state machine to all critical devices that have multiple hardware checkpoints and comparators. It is important to note that FRIB is a cw machine and MPS status is continuously being monitored by 'device mode change' and real time data link. In this paper, we present FRIB Machine Protection architecture, plans and implementation.

 
TUP029 Continued Monitoring of the Conditioning of the Fermilab Linac 805 MHz Cavities cavity, linac, booster, site 464
 
  • E.S.M. McCrory, F.G. Garcia, T.K. Kroc, A. Moretti, M. Popovic
    Fermilab, Batavia
 
 

We have been collecting data on the conditioning of the high-gradient accelerating cavities in the Fermilab 400 MeV H-Minus Linac for over 16 years [1]. This linac was upgraded in 1989 from a 201 MHz Alverez structure to include 805 MHz side-coupled cavities. Automated measurements of the sparking rate have been recorded since 1994 and are reported here. The sparking rate has declined since the beginning, but there are indications that this rate may have leveled off now. The X-rays emitted by the cavities are continuing to decrease.


[1] Kroc, et al., Proceedings of LINAC96, pp 338-340

 
TUP069 Radiation from the SDTL of J-PARC radiation, simulation, linac, DTL 569
 
  • F. Naito, K. Nanmo, H. Tanaka
    KEK, Ibaraki
  • H. Asano, T. Ito
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
 
 

X-ray radiation from the SDTL of J-PARC linac has been observed with the beam loss monitor by the cavity. The results show that the X-ray intensity depends not only on the RF power level of the tank but also on the RF structure of the tank. In the paper we will show the results of the investigation for the origin of the X-ray radiation from the tank.

 
TUP075 Residual Gas Pressure Dependence of Beam Loss linac, radiation, vacuum, ion 587
 
  • A. Miura, M. Ikegami
    JAEA/J-PARC, Tokai-mura
  • H. Sako
    JAEA, Ibaraki-ken
  • G.H. Wei
    KEK/JAEA, Ibaraki-Ken
 
 

Residual gas in beam transport line essentially affects the beam loss and residual radiation on the accelerator. J-PARC linac is usually operated under 1.0 ·10-6 to 1.0 ·10-5 Pa in SDTL and A0BT sections. In this situation, no serious beam loss was observed during the beam operation. In future development of J-PARC linac, because the peak beam energy and output will be increased, it is getting more serious problem. Before the development, it is important to understand a cause of beam loss and relation between beam loss and residual gas pressure. We measured beam loss at the normal and worse vacuum condition in both SDTL and A0BT sections. The result indicates that the beam loss depends on the residual gas pressure and position where the beam loss occurs is about 20 to 30 meter downstream. This suggests the optimum position for installation of vacuum system to minimize the beam loss. In this paper, we describe the experimental result and its discussions. In addition, the cause of the beam loss is considered to be a stripping from negative hydrogen ions to neutral hydrogen atoms. This mechanism is also discussed in this paper.

 
TUP076 Status of Beam Loss Evaluation at J-PARC Linac linac, proton, cavity, background 590
 
  • A. Miura, N. Kikuzawa, T. Maruta, K. Yamamoto
    JAEA/J-PARC, Tokai-mura
  • Z. Igarashi, T. Miyao
    KEK, Ibaraki
  • M. Ikegami
    J-PARC, KEK & JAEA, Ibaraki-ken
  • H. Sako
    JAEA, Ibaraki-ken
  • S. Sato
    JAEA/LINAC, Ibaraki-ken
 
 

Since November, 2007, J-PARC Linac has been operated at 7.2kW beam power. During the operation, beam losses possibly caused by the H0 particles generated by the interaction between H- beam and residual gas in the transport line were observed in the SDTL (Separated-type Drift-Tube Linac) section. In the linac operation, Ar-CO2 gas proportional counters are employed for the measurement of beam loss, but they are also sensitive to background noise of X-ray emitted from RF cavities. In this section, protons, secondary hadrons and gamma rays would be mainly generated as a beam loss, but it is not easy to estimate real beam loss using the proportional counter. The plastic scintillation counters with less X-ray sensitivity and 3He proportional counters with high thermal neutron sensitivity will be also employed to measure the beam loss. The combination of these detectors would bring more accurate beam loss measurements with suppression of X-ray noise. A measurement of emission position and angle distributions of protons due to H- beam loss is being planed. This result would lead to clarify the source of beam loss. This paper reports status of beam loss evaluation using these detectors.

 
THP088 Simulation Study of Debuncher System for J-PARC Linac Energy Upgrade linac, injection, simulation, controls 947
 
  • G.H. Wei
    KEK/JAEA, Ibaraki-Ken
  • M. Ikegami
    KEK, Ibaraki
 
 

On the beam line after linac in high power proton accelerators, like J-PARC, debuncher system plays an important role for beam injection to the succeeding ring. The debuncher system usually gives two functions, namely, to correct the center energy jitter and to minimize momentum spread and adjust beam energy at the injection. To mitigate the nonlinear effects of RF field, a debuncher system with two debuncher cavities was designed for the 181-MeV operation of J-PARC linac. In this design, the first debuncher is expected to deal with center energy jitter. Then, the second debuncher is utilized to control the injection momentum spread according to the requirements from the ring. Although the debuncher system was originally designed to minimize the momentum spread, beam-commissioning results show a different requirement for the injection momentum spread to minimize the beam loss in the ring. Based on the original design and the experimental findings with 181-MeV operation, we have designed a debuncher system for the energy upgrade of J-PARC linac to 400 MeV. In this paper, the beam dynamics design of the new debuncher system is presented together with some particle simulation results.

 
THP091 Simulations of Ion Beam Loss in RF Linacs with Emphasis on Tails of Particle Distributions linac, rfq, simulation, bunching 956
 
  • D. Berkovits, B. Bazak, G. Feinberg, I. Mardor, J. Rodnizki, A. Shor, Y. Yanay
    Soreq NRC, Yavne
 
 

Design of ion linacs with ion currents of several milli-amps necessitates detailed simulations of beam loss. At high intensities, even a small amount of beam loss can result in significant radio-activation of the linac components. Particle loss can result from longitudinal tails created in the bunching and pre-accelerating process, whereas strong transverse focusing and collimation limit the development of a transverse tail. In modern RF ion linacs, bunching and pre-acceleration take place in a radio frequency quadrupole (RFQ). We present a new approach for beam loss calculations that places emphasis on the tails of the particle distributions. This scheme is used for simulating the SARAF proton/deuteron linac, a 176 MHz complex designed to operate in CW mode at 4 mA beam current. We describe implementation of a RFQ accelerating element in the GPT 3D simulation code. We discuss our scheme for highlighting the tails of the particle distributions generated by the RFQ. These distributions are used as input to simulations of the RF superconducting linac, where subsequent particle loss is calculated. This technique allows us to increase beam loss statistics by a significant factor.