ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
The concept of an ultra-low transverse emittance injector operating in CW mode for an XFELO* was discussed at LINAC-08**. Here we will report the design optimization of the injector, which includes a 100 MHz RF-gun with thermionic cathode, an energy filter to produce short bunches (~0.5 nsec), a velocity bunching section, higher harmonic cavities to minimize longitudinal emittance, two bunch compressors and accelerating sections operating at 400 MHz and 1300 MHz to obtain 540 MeV electrons. The proposed design is capable of producing 40 pC bunches with 0.5 psec rms time width and 0.7 MeV rms energy spread. Most significantly, the transverse rms emittance is kept below 0.11 π μm. The longitudinal emittance and bunch time width can be substantially reduced for low-charge bunches of several pC.
*K.-J. Kim, Y. Shvyd’ko, and S. Reiche, Phys. Rev. Lett., 100 244802 (2008).
**P.N. Ostroumov, K.-J. Kim, Ph. Piot, Proceedings of the Linac-2008.
ANL, Argonne
GANIL, Caen
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
We have developed and tested an X-ray based Bunch Length Detector (XBLD) for application in ion accelerators. X-rays produced as a result of ion beam interactions with matter are used to generate photoelectrons. The photoelectrons are analyzed by an rf deflector synchronized with the master oscillator, similar to the BLDs based on secondary electrons. The expected time resolution is several picoseconds. The proposed XBLD is particularly useful for the measurement of cw heavy-ion beams passing through a stripper foil or film in a high-power driver accelerator. The results of the XBLD commissioning and beam bunch profile measurements at the ANL heavy-ion cw ATLAS accelerator will be presented.
ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
The development of a uniform and stable high velocity, thin liquid lithium film stripper is essential for the Facility for Rare-Isotope Beams (FRIB) Project. The formation of such a film has been demonstrated recently at ANL. Film thickness should be measured, and its temporal and spatial stability under high power ion beam irradiation should be verified. Intense beams of light ions generated by the FRIB prototype injector can be used for this task. The injector consists of an ECR ion source followed by a LEBT. A DC 3.3 mA/75 kV proton beam has been generated at the LEBT output. Proton beam power will be brought to required level by adding the second acceleration tube. A low energy electron beams (LEEB) technique, based on the thickness-dependent scattering of the electrons by the film, has been proposed as a fast-response on-line film thickness monitoring. A LEEB test bench has been built to verify this technique. The transmission of electrons through the carbon foils of different thicknesses was measured and compared with results of CASINO simulations. Agreement between the experimental and numerical results allows quantitative measurements of film thickness using the LEEB.
ANL, Argonne
Fermilab, Batavia
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
The latest version of PTRACK*, the parallel version of the beam dynamics code TRACK, is capable of simulating a very large number of particles (a billion or more). In the case of the Fermilab 8-GeV H-minus linac, it is possible to simulate the actual number of particles in the bunch. Taking advantage of this capability we are revisiting our original beam loss studies**, but this time with larger statistics and including a new process of beam loss which is the stripping of H- ions. TRACK has recently been updated*** with the possibility of stripping H- by three different processes, namely black body radiation, Lorentz force stripping and residual gas interactions. Results of ideal end-to-end simulations (no errors) with the actual number of particles in a beam bunch (860M) as well as error simulations for different sets of errors with 10M and eventually 100M particles per seed will be presented and discussed. These simulations are being performed on Argonne's new petascale computing facility "BG/P".
* J. Xu et al, Proceedings of HB-2008.
** P. Ostroumov, B. Mustapha and V.A. Aseev, Proceedings of Linac-06.
*** J.-P. Carneiro, B. Mustapha and P. Ostroumov, submitted to PRST-AB.
ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
Kinetic space plasma simulations are dominated by PIC (Particle-In-Cell) codes. Due to the inherent noise in PIC simulations, interest in directly solving the Vlasov equation is increasing. With the fast development of supercomputers, this is becoming more realistic. We present our preliminary work on solving the Vlasov equation for beam dynamics simulations*. A high order Spectral Element Method has been applied to achieve high accuracy, easy interpolation, and parallelization. Due to the inherent instability of the Vlasov equation, a spectral filter has been added and mass conservation has been satisfied. The proposed algorithms were validated on 1D1V simulations. A paraxial model of the Vlasov equation (2D2V) has also been studied and compared with PIC simulations at ANL using the BG/P supercomputer.
*J. Xu, P. Ostroumov and J. Nolen, “Highly Scalable Parallel Algorithm for 2D2V Vlasov Equation with High Order Spectral Element Method”, poster on SC08, Austin, Texas, Nov.15-20, 2008.
ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
The corrective steering algorithm in TRACK has been recently updated to be more realistic. A simplified formalism will be presented along with the method of implementation. As an important application, the algorithm was used to determine the number of correctors and monitors required for the front-end of the HINS project at Fermilab. The algorithm allowed us also to find the optimum locations for the correctors and monitors as well as the required corrector field strength and the required monitor precision for an effective correction. This correction procedure could be easily implemented in an accelerator control-room for real-time machine operations.
ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
An energy upgrade project of the ATLAS heavy ion linac at ANL includes a new cryomodule containing seven {10}9 MHz β=0.15 quarter-wave superconducting cavities to provide an additional 15 MV voltage to the existing linac. Several new features have been incorporated into both the cavity and cryomodule design. For example, the primary feature of the cryomodule is a separation of the cavity vacuum space from the insulating vacuum. The cavities are designed in order to cancel the beam steering effect due to the RF field. The cryomodule was designed and built as a prototype for the driver linac of the Facility for Rare Isotope Beams (FRIB). Similar design can be effectively used in the SC proton linac for the Project X at FNAL. Currently, we are working on cryomodule assembly and final preparation of cryogenics, RF, vacuum and other subsystems for off-line tests. The initial commissioning results will be reported.
Fermilab, Batavia
NSCL, East Lansing, Michigan
ANL, Argonne
A superconducting cavity has been designed for acceleration of particles traveling at 81% the speed of light (beta = 0.81). The application of interest is an 8 GeV proton linac proposed for a Fermilab upgrade; at present, the cavity is to be used from 420 MeV to 1.3 GeV. The cavity is similar to the 805 MHz high-beta cavity developed for the SNS Linac, but the resonant frequency (1.3 GHz) and beam tube diameter (78 mm) are the same as for the beta = 1 cavities developed for the TESLA Test Facility. Four single-cell prototype cavities have been fabricated and tested. Two multi-cell prototypes have also been fabricated, but they have not yet been tested. The original concept was for an 8-cell cavity, but the final design and prototyping was done for 7 cells. An 11-cell cavity was proposed recently to allow the cryomodules for the beta = 0.81 cavity and downstream 9-cell beta = 1 cavities to be identical. The choice of number of cells per cavity affects the linac design in several ways. The impact of the number of cells in the 8 GeV linac design will be explored in this paper. Beam dynamics simulations from the ANL code TRACK will be presented.