Fermilab, Batavia
ANL, Argonne
IUCF, Bloomington, Indiana
Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The High Intensity Neutrino Source (HINS) linac R&D program at Fermilab aims to construct and operate a first-of-a-kind, 60 MeV, superconducting H- linac. The machine will demonstrate acceleration of high intensity beam using superconducting spoke cavities from 10 MeV, solenoidal focusing optics throughout for axially-symmetric beam to control halo growth, and operation of many cavities from a single high power rf source for acceleration of non-relativistic particles.
Fermilab, Batavia
ANL, Argonne
Fermilab is designing and building the HINS front-end test facility. The HINS proton linear accelerator consists of a normal-conducting and a superconducting section. The normal-conducting (warm) section is composed of an ion source, a 2.5 MeV radio frequency quadrupole (RFQ), a medium energy beam transport, and 16 normal-conducting crossbar H-type cavities that accelerate the beam to 10 MeV. Production of 325 MHz 4-vane RFQ is recently completed. This paper presents the design concepts for this RFQ, the mechanical design and tuning results. Issues that arose during manufacturing of the RFQ will be discussed and specific corrective modifications will be explained. The preliminary results of initial testing of RFQ at the test facility will be presented and comparisons with the former simulations will also be discussed.
ANL, Argonne
ORNL, Oak Ridge, Tennessee
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC-02-06CH11357.
In an effort to simulate the SNS linac using the beam dynamics code TRACK and to benchmark the results against the recent commissioning data, we have started updating TRACK to support SNS-type elements such as DTL's and CCL's. After successfully implementing and simulating the DTL section of the SNS linac*, we have implemented the CCL section and the high energy superconducting (SC) section up to 1 GeV. Results from end-to-end simulations of the SNS linac using TRACK will be presented and compared to simulations using other codes and to the recent commissioning data.
*"First TRACK Simulations of the SNS linac", B. Mustapha et al., in Proceedings of Linac-06 Conference, Knoxville, Tennessee, August 21-25, 2006.
ANL, Argonne
Northern Illinois University, DeKalb, Illinois
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357.
We have developed a pepper pot - scintillator screen system to measure the emittance of low-energy dc beams extracted from an ECR ion source and post-accelerated to an energy of 75 - 90 keV/charge. Different scintillators have been tested and CsI (Tl) was chosen due to its high sensitivity, wide dynamic range and long life-time. The linearity of both the scintillator and the CCD camera has been studied. A LabVIEW code has been developed and used for on-line emittance measurements. Un-normalized rms emittances measured for 209Bi20+ and 209Bi21+ beams with current of 1.0 - 1.5 pnA are usually ~30 π mm.mrad. A complicated structure of multiple images of individual holes has been observed. The innovative combination of a special type of scintillator, a CCD camera and a fast shutter allowed us to create a very efficient emittance meter for low-energy dc ion beams. Using on-line emittance measurements, it was possible to improve the beam quality by re-tuning the ion source conditions. Because of the two-dimensional array of holes in the pepper-pot, this emittance meter can be used to observe and study four-dimensional emittance correlations in beams from ECR ion sources.
ANL, Argonne
Northern Illinois University, DeKalb, Illinois
Funding: This work was supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC-02-06CH11357.
An XFELO proposed recently* requires a continuous sequence of electron bunches with ultra-low transverse emittance less than 0.1 mm-mr, a bunch charge of 40 pC, an rms energy spread of 1.4 MeV, repeating at a rate between 1 MHz to 100 MHz. The bunches are to be compressed to an rms lengths less than 2 ps at the final energy of 7 GeV. Following the successful commissioning of the pulsed injector based on a thermionic gun** we discuss a concept for ultra-low emittance injector to produce 100 MHz CW electron bunches. The electron beam is extracted by ~1MV rf voltage using low frequency ~100 MHz room temperature rf cavity. The injector also includes a chicane and slits to form a short ~1 nsec bunch, a pre-buncher a booster buncher to form low longitudinal emittance of the bunched beam, an accelerating section to ~50 MeV using higher harmonic cavities, and an rf cosine-wave chopper to form any required bunch repetition rate between 1 MHz and 100 MHz. The results of initial optimizations of the beam dynamics with the focus on extracting and preserving ultra-low emittance will be presented.
*K.-J. Kim, Y. Shvyd'ko, and S. Reiche, to be published in Physical Review Letters (2008)
**K. Togawa, et al., Phys. Rev. STAB 10, 020703 (2007)
ANL, Argonne
Northern Illinois University, DeKalb, Illinois
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC-02-06CH11357.
A prototype injector capable to produce multiple-charge-state heavy-ion beams is being developed at ANL. The injector consists of an ECR ion source, a 100 kV platform and a Low Energy Beam Transport (LEBT). The latter comprises two 60-degree bending magnets, electrostatic triplets and beam diagnostics stations. Several charge states of bismuth ions from the ECR have been extracted, accelerated to an energy of 1.8 MeV, separated and then recombined into a high quality beam ready for further acceleration. This technique allows us to double heavy-ion beam intensity in high-power driver linac for future radioactive beam facility. The other application is the post-accelerators of radioactive ions based on charge breeders. The intensity of rare isotope beams can be doubled or even tripled by the extraction and acceleration of multiple charge state beams. We will report the results of emittance measurements of multiple-charge state beams after recombination.
ANL, Argonne
Fermilab, Batavia
Funding: This work was supported by the U.S. Department of Energy, Office of Scince, under contracts number DE-AC02-06CH11357 and No. W-31-109-ENG-38.
The proposed 8 GeV proton driver (PD) linac at FNAL includes a front end up to ~420 MeV and a high energy section operating at 325 MHz and 1300 MHz respectively. A normal conducting RFQ and short H-type resonators are being developed for the initial acceleration of the H-minus or proton beam up to 10 MeV. From 10 MeV to ~420 MeV the voltage gain is provided by SC spoke-loaded cavities. In the high-energy section, the acceleration will be provided by the International Linear Collider (ILC)-style SC elliptical cell cavities. To employ the existing readily available klystrons, an rf power fan out from high-power klystrons to multiple cavities is being developed. The beam dynamics simulation code TRACK available in both serial and parallel versions has been updated to include H-minus stripping due to all known mechanisms to predict the exact location of beam losses. An iterative procedure has been developed to interact with the transient beam loading model taking into account feedback and feedforward systems applied for the rf distribution from one klystron to multiple cavities.
ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC-02-06CH11357.
Accelerator simulations still do not provide everything designers and operators need to deploy a new facility with confidence. This is mainly because of limitations preventing realistic, fast-turnaround, end-to-end simulations of the beam from the source all the way through to a final interaction point and because of limitations in on-line monitoring that prevent a full characterization of the actual beam line. As a result, once a machine is built there can be a gap between the expected behavior of the machine and the actual behavior. This gap often corresponds to enormous work and significant delays in commissioning a new machine. To address the shortcomings of the existing beam dynamics simulation codes, and to fulfill the requirements of future hadron and heavy-ion machines, a starting point for a realistic simulation tool is being developed at ANL that will support detailed design evaluation and also fast turnaround computation to support commissioning and operation of the facility. The proposed simulations will be performed on the fast growing computing facility at ANL with peta-scale capability.
ANL, Argonne
A set of six new 109 MHz β=0.15 superconducting quarter-wave resonators (QWR) has been built at ANL as part of an upgrade to the ATLAS superconducting heavy-ion linac. The final cavity string assembly will also use many of the techniques needed for the next generation of large high-performance ion linacs such as the U.S. Department of Energy's FRIB project. Single-cavity cold tests at T=4.5 K have been performed for three cavities with moveable coupler, rf pickup, and VCX fast tuner as required for the full 6-meter cryomodule assembly. The average maximum accelerating gradient of 4 cavities (3 new + 1 prototype), is EACC=11.2 MV/m (BPEAK=65 mT). Clean cavity string assembly techniques, required here and for most future SRF ion linacs, are fairly well developed. Details on cavity performance including high-field cw operation, microphonics and fast tuning are presented.