A high energy beam absorber has been built for the Advanced Superconducting
Test Accelerator (ASTA) at Fermilab. In the facility's initial configuration,
an electron beam will be accelerated through 3 TTF-type or ILC-type RF
cryomodules to an energy of 750MeV. The electron beam will be directed to one
of multiple downstream experimental and diagnostic beam lines and then
deposited in one of two beam absorbers. The facility is designed to accommodate
up to 6 cryomodules, which would produce a 75kW beam at 1.5GeV; this is the
driving design condition for the beam absorbers. The beam absorbers consist of
water-cooled graphite, aluminum and copper layers contained in a Helium-filled
enclosure. This paper describes the mechanical implementation of the beam
absorbers, with a focus on thermal design and analysis. In addition, the
potential for radiation-induced degradation of the graphite is discussed.Comment: 3 pp. 3rd International Particle Accelerator Conference (IPAC 2012)
  20-25 May 2012. New Orleans, Louisian

Baffes, C.

Church, M.

Leibfritz, J.

Oplt, S.

Rakhno, I.

English

arXiv

A high energy beam absorber has been built for the Advanced Superconducting Test Accelerator (ASTA) at Fermilab. In the facility's initial configuration, an electron beam will be accelerated through 3 TTF-type or ILC-type SRF cryomodules to an energy of 750MeV. The electron beam will be directed to one of multiple downstream experimental and diagnostic beam lines and then deposited in one of two beam absorbers. The facility is designed to accommodate up to 6 cryomodules, which would produce a 75kW beam at 1.5GeV; this is the driving design condition for the beam absorbers. The beam absorbers consist of water-cooled graphite, aluminum and copper layers contained in a helium-filled enclosure. This paper describes the mechanical implementation of the beam absorbers, with a focus on thermal design and analysis. The potential for radiation-induced degradation of the graphite is discussed

UNT Digital Library

 MECHANICAL DESIGN OF A HIGH ENERGY BEAM ABSORBER FOR THE ADVANCED SUPERCONDUCTING TEST ACCELERATOR (ASTA) AT FERMILAB* C. Baffes**, M. Church, J. Leibfritz, S. Oplt, I. Rakhno, FNAL, Batavia, IL 60510, USA  Abstract A high energy beam absorber has been built for the Advanced Superconducting Test Accelerator (ASTA) at Fermilab.  In the facility’s initial configuration, an electron beam will be accelerated through 3 TTF-type or ILC-type SRF cryomodules to an energy of 750MeV.  The electron beam will be directed to one of multiple downstream experimental and diagnostic beam lines and then deposited in one of two beam absorbers.  The facility is designed to accommodate up to 6 cryomodules, which would produce a 75kW beam at 1.5GeV; this is the driving design condition for the beam absorbers. The beam absorbers consist of water-cooled graphite, aluminum and copper layers contained in a helium-filled enclosure.  This paper describes the mechanical implementation of the beam absorbers, with a focus on thermal design and analysis.  The potential for radiation-induced degradation of the graphite is discussed.    Introduction Fermi National Accelerator Laboratory is constructing the Advanced Superconducting Test Accelerator (ASTA), a 750MeV electron linac intended to develop and test the technology that will be required for next-generation high-intensity linear accelerators, such as Fermilab’s Project X [1] and the ILC.   ASTA is housed within the SRF Accelerator Test Facility [2], which, when complete, will also incorporate a cryogenic plant, cryomodule testing facilities, and space for planned future experiments.  ASTA will consist on an electron gun, injector, 3 TTF-type or ILC-type cryomodules, downstream diagnostic and experimental beam lines, and a high energy beam dump.  The beam dump contains two beam absorbers; one for each of the experimental beam lines.  The absorbers are designed to accommodate a future upgrade to the facility, in which a beam would be accelerated through 6 cryomodules.  The beam parameters provided by this upgraded machine drive the absorber design, and are shown in the table below: Table 1: 6-Cryomodule ASTA Key Beam Parameters Species e- Beam Energy 1.5 GeV Bunch Charge 3.3 nC Pulse Characteristics 1 ms duration @ 5Hz Bunches per Pulse 3000 Total Average Power 75 kW Beam Transverse Size Dia 3mm RMS (σ=1.5mm) Absorber Configuration The beam absorbers must terminate the beam and reject its power to cooling water.  The high thermal load, radiation environment, and the need to achieve high reliability were key considerations in the design.  A section view of an absorber is shown in Figure 1.  The beam exits the beamline through a vacuum window, and is then incident on a stack of graphite with transverse dimensions 0.2 X 0.2m and length 0.9m along the beamline.  Downstream of the graphite are aluminum, copper and steel “core” plates.  The total length of the absorber along the beam direction is 2m.  The graphite and the aluminum core plates are sandwiched between water-cooled gun-drilled aluminum cooling plates.  All components of the system are conductively coupled to these cooling plates.  The most sensitive components are the aluminum core plates just downstream of the graphite; an indium foil was used in this location to ensure good thermal coupling to the cooling plates.  Beam power is rejected through the cooling plates to a radioactive-water closed-loop cooling skid circulating 30 gallons per minute through each absorber.     Figure 1: Absorber Configuration: graphite shown in dark grey, aluminum shown in light gray/blue, copper shown in orange, steel shown in purple.  Beam enters from right.    In order to prevent oxidization of the graphite and the formation of corrosive compounds due to beam interaction with air, the absorbers are housed within stainless steel enclosures filled with helium at a slight  ______________________________________________ * Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the United States Department of Energy ** cbaffes@fnal.gov pptwtAmFtmrwvbtmpMositive pressuThe interasignificant prorotect the fache beam dumith overall ootal weight of GrDuring exdamage due tolattice. At damtom (DPA) dexperienced stsignificant chauch lower dapplication arconductivity. When usgraphite has bdamage level,or the type absorber, datadamage domransition fromlevel of 15 shrinkage of application, daaterial woulegime.  In oshrinking occuloaded onto tashers that graphite radiatRadiation conductivity conductivity calue.  This dlattice interrupoundaries [5]able to selfconductivity chermal conduon the irradiatiGiven the odeled usincalculated in uanalyses reveaabsorber in orIntegrating ovconservative d(20 years of fu3-Dimensionaldeveloped (seeIn order tgraphite coreroperties for uch data exire relative to action of beam mpt and resiility and its op consist of utside dimens approximatelyaphite Radposure to the dislocation oage levels aue to proton bructural failurnges in mateamage levelse changes ined in radiatieen shown t and then swof isotropic  generated froinated by n shrinking to DPA after approximatelymage levels wd be expectedrder to mainrs, the aluminhe graphite will limit preion shrinkage damage is alsoof graphite. an drop to a egradation is tting phonon t.  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Mechanical Design of a High Energy Beam Absorber for the Advanced Superconducting Test Accelerator (ASTA) at Fermilab

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