Ammigan K

Atherton AR

Butcher M

Calviani M

Caretta O

Davenne TR

Densham CJ

Fitton MD

Guinchard M

Hartsell BD

Hurh P

Kuksenko VI

Losito R

Loveridge P

O'Dell J

Roberts SG

Zwaska RM

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EXAMINATION OF BERYLLIUM UNDER INTENSE HIGH ENERGYPROTON BEAM AT CERN’S HIRADMAT FACILITY∗K. Ammigan†, B. Hartsell, P. Hurh, R. Zwaska, FNAL, Batavia, IL 60510, USAA. Atherton, O. Caretta, T. Davenne, C. Densham, M. Fitton, P. Loveridge, J. O’Dell,RAL, Didcot, UKS. Roberts, Oxford University, Oxford, and CCFE, Culham, UKV. Kuksenko, Oxford University, Oxford, UKM. Butcher, M. Calviani, M. Guinchard, R. Losito, CERN, Geneva, SwitzerlandAbstractBeryllium is extensively used in various accelerator beamlines and target facilities as material for beamwindows, andto a lesser extent, as secondary particle production targets.With increasing beam intensities of future accelerator facil-ities, it is critical to understand the response of berylliumunder extreme conditions to avoid compromising particleproduction efficiency by limiting beam parameters. As aresult, the planned experiment at CERN’s HiRadMat facil-ity will take advantage of the test facility’s tunable high in-tensity proton beam to probe and investigate the damagemechanisms of several grades of beryllium. The test ma-trix will consist of multiple arrays of thin discs of varyingthicknesses as well as cylinders, each exposed to increas-ing beam intensities. Online instrumentations will acquirereal time temperature, strain, and vibration data of the cylin-ders, while Post-Irradiation-Examination (PIE) of the discswill exploit advanced microstructural characterization andimaging techniques to analyze grain structures, crack mor-phology and surface evolution. Details on the experimentaldesign, online measurements and planned PIE efforts aredescribed in this paper.INTRODUCTIONBeryllium is currently widely used as the material ofchoice for beamwindows, as well as secondary particle pro-duction targets, in many accelerator beam lines and targetfacilities. With the increasing beam intensities of future ac-celerators [1,2], it is essential to evaluate the performanceofberyllium under even more extreme conditions to success-fully design and reliably operate windows and targets, with-out compromisingparticle production efficiency by limitingbeam parameters.An upcoming experiment at CERN’s HiRadMat facility[3] will test beryllium specimens exposed to intense protonbeams. The test facility is able to deliver high intensity pro-ton beams, up to 4.9 ×1013 protons per 7.2 μs pulse (288bunches), with a Gaussian beam sigma ranging from 0.1mm to 2 mm [4]. The main objectives of the experimentare to explore the onset of failure modes of beryllium un-der controlled conditions at highly localized strain rates and∗ Work supported by Fermilab - Operated by Fermi Research Alliance,LLC, under Contract No. DE-AC02-07CH11359 with the U.S. Depart-ment of Energy† ammikav@fnal.govtemperatures, identify any thermal shock limits, and vali-date highly non-linear numerical models with experimentalmeasurements.EXPERIMENTAL SET-UPThe test rig is based on a double containment design toensure containment of the beryllium specimens and any po-tential radioactive contamination created from beam inter-action. The specimens will be arranged in four horizontalarrays aligned vertically in a single column. Figure 1 showsthe test chamber positioned on the HiRadMat mobile table.Figure 1: Test chamber positioned on mobile table.The experiment chamber is an outer containment box,which encloses the specimen inner containment boxes.Small apertures on the outer box allow the beam to enterand exit, using a shutter system to provide post-experimentcontainment. Additionally, the internal volume of the outerchamber is continuously evacuated by a pump which drawsthe air out of the box via a HEPA filter (not shown in Figure1). The continuous pumping and lower pressure within theouter chamber ensures no airborne particulate escapes thecontainment box. The HEPA filter will be analyzed uponcompletion of the experiment to check for any containmentbreach of the array boxes.Specimen HousingAs shown in Figure 2, each specimen type within an ar-ray is enclosed in a separate containment box, sealed withglassy carbon beam windows [5]. Gafchromic foils are po-Proceedings of IPAC2015, Richmond, VA, USA WEPTY0157: Accelerator TechnologyT20 - TargetryISBN 978-3-95450-168-73289 Copyright©2015CC-BY-3.0andbytherespectiveauthorssitioned in front of each array to verify beam alignmentduring pilot beam pulses. The optical windows allow forvisual monitoring of the experiment as well as for LaserDoppler Vibrometer (LDV) measurements of surface defor-mation/vibration of the slug specimens.Figure 2: Interior of experiment chamber.Material SpecimensTwo types of specimens are included in the experiment:thin discs for deformation, strain, and crack/failure analysesduring PIE, and slugs for real time measurements of strain,temperature, and vibration (Figure 3). A few thin discswill be pre-characterized by Electron Backscatter Diffrac-tion analysis (EBSD), and are only placed in Arrays 1 and 4(Figure 4). The slugs in each array are slightly offset fromthe upstream thin discs so that the beam impacts the slugsclose to the cylindrical edge.Figure 3: Specimen types: thin discs and slugs.InstrumentationInstrumentation for real-time data acquisition will in-clude strain gauges, temperature sensors, an LDV system,and cameras. The gauges, attached to the external cylin-drical surface of the slugs, will measure the temporal cir-cumferential strain and temperature response induced bythe beam, while the LDV will record dynamic radial defor-mations. The online measurements will help validate theberyllium strength and damage models, as well as identifyelastic-plastic regime structural response. Cameras will beused for visual monitoring of the experiment, and to imagethe Gafchromic foils for beam alignment purposes. A beamposition monitor (BPKG) will also aid in beam alignment.EXPERIMENTAL PARAMETERSThe experimental beam parameters were guided by nu-merical simulations, to incrementally push beryllium to itsmaterial failure limit. Particle-matter interaction simula-tions were performed with the MARS15 code [6] to obtainenergy deposition in the specimens, as a function of beamsigma and intensity. After accounting for probable numeri-cal and experimental uncertainties, a beam spot size of σ =0.3 mmwas chosen so that the expected local peak tempera-ture rise (ΔT∼ 1025 ◦C) does not exceed thematerial’smelt-ing point (1290 ◦C) for the highest intensity beam pulse.Test MatrixFigure 4 shows the composition of each array as wellas the predetermined beam intensities. The four berylliumgrades include the S-65F, S-200F, S-200FH, and PF-60grades, which differ in impurity content, consolidation pro-cess, yield strength, and ductility. Array 2 is subjected totwo pulses separated vertically, while array 3 receives mul-tiple pulses at the same location.Figure 4: Test matrix illustrating the specimen type, size,grade, and incident beam intensities (1.7×1011 protons perbunch).Beam Induced Stress and StrainThe nearly instantaneous local temperature jump due tobeam interaction, and the resulting large temperature gra-dients induce strong thermal shock in the specimens. LS-DYNA FEA models [7] were therefore set up to evaluatethe beam induced stresses and strains, as a function of beamintensities, and specimen thicknesses. The contour plot inFigure 5 shows the residual effective strain distribution ina thin disc specimen after being exposed to a maximum in-tensity beam pulse.Figure 5: Effective strain contour plot from a 2D axisym-metric model (0.75 mm disc after cool-down).The peak residual effective strain is shown to be around3%, which is larger than beryllium failure strains (∼2% forS-200F VHP at RT) given in the literature [8]. Therefore,for this particular disc, interior cracking or fracture of theWEPTY015 Proceedings of IPAC2015, Richmond, VA, USAISBN 978-3-95450-168-73290Copyright©2015CC-BY-3.0andbytherespectiveauthors7: Accelerator TechnologyT20 - Targetrydisc in the area of large plastic deformation is expected. Per-manent out-of-plane deformations on both faces of the discis also expected. Figures 6 and 7 show the range of peakresidual effective strain and out-of-plane deformation ex-pected from the discs in the test matrix, as a function ofdisc thickness and beam intensity.50 100 150 200 250 30000.511.522.533.5Effective strain vs. intensity(σ = 0.3 mm, after cool−down)Intensity (bunches)Effective total strain (%)t = 0.25 mmt = 0.75 mmt = 2 mmFigure 6: Peak residual effective strain after cool-down.50 100 150 200 250 3000123456789x 10−6Permanent deformation vs. intensity(σ = 0.3 mm, after cool−down)Intensity (bunches)Out−of−plane displacement (m)t = 0.25 mmt = 0.75 mmt = 2 mmFigure 7: Peak out-of-plane surface deformation after cool-down.Array 3will explore strain and deformation accumulationdue to cyclic loading resulting from multiple beam pulses.Figure 8 reveals how the peak effective strain increases withconsecutive pulses, with plastic strain shakedown expectedto occur after more than 20 pulses.POST-IRRADIATION-EXAMINATIONAfter sufficient cool-down time, assessed by FLUKA ra-diological simulations [9], the outer containment box willbe disassembled. The inner containment boxes will theneach be removed and transported to Oxford University andthe Culham Center for Fusion Energy (CCFE) facility inthe UK for PIE. Visual Light and Scanning Electron Mi-croscopy (SEM) will be used for microstructural character-ization of the thin discs. The composition and crystallo-graphic maps in the beam spot area of the discs will be builtwith the Energy-Dispersive X-ray spectroscopy and EBSDtechniques and the correlation between the thermal shockconsequences and the microstructural features of the differ-ent beryllium grades will be explored. Focused Ion Beam0 10 2000.0050.010.0150.020.0250.03Maximum effective strain (t = 0.75 mm)(20 x 144b)Number of pulsesEffective strain (m/m)Figure 8: Effective strain accumulation in 0.75 mm discfrom multiple beam pulses.system will be used for crack investigation in 3D. Finally,the out-of-plane deformation will be measured by profilom-etry technique and compared with the FEA numerical pre-dictions.CONCLUSIONSUnderstanding beryllium material behavior under ex-treme conditions is critical to the reliable design and oper-ation of future high intensity accelerator facilities. This ex-periment has been designed to test and push beryllium to itsfailure limit, in an effort to evaluate thermal shock responseand probe the failure and damage mechanisms of differentgrades of the material. The experiment, called HRMT-24BeGrid, is scheduled for week 38 (Sept. 14th) in 2015 [4],with results expected within a year of irradiation.REFERENCES[1] Fermilab’s Long Baseline Neutrino Experiment (LBNE),http://lbne.fnal.gov/[2] Calviani, M. et al., “Specification for the Renovated NorthArea Primary Targets T2, T4, T6, T10 and Associated BeamInstrumentation”, CERN EDMS No. 1267311, SPS-T-ES-0001, (2014).[3] I. Efthymiopoulos, C. Hessler, H. Gaillard, D. Grenier, M.Meddahi, P. Trilhe, A. Pardons, C. Theis, N. Charitonidis, S.Evrard, H. Vincke and M. Lazzaroni, “HiRadMat: A New Ir-radiation Facility for Material Testing at CERN, Proceedingsof IPAC 2011”,TUPS058, San Sebastien, Spain, 4-9 Septem-ber (2011).[4] High-Radiation to Materials (HiRadMat) Facility at CERNSPS, https://espace.cern.ch/hiradmat-sps/[5] Tokai Co. LTD, Features and Properties of Glassy Carbon,http://www.tokaicarbon.co.jp/en/products/fine_carbon/gc.html[6] N.V. Mokhov, K.K. Gudima, C.C. James et al., “Recent En-hancements to the MARS15 Code”, Fermilab-Conf-04/053(2004), http://www-ap.fnal.gov/MARS/[7] LS-DYNA Keyword User’s Manual, Livermore SoftwareTechnology Corporation, Vol. 1, rev. 5471 (2014).Proceedings of IPAC2015, Richmond, VA, USA WEPTY0157: Accelerator TechnologyT20 - TargetryISBN 978-3-95450-168-73291 Copyright©2015CC-BY-3.0andbytherespectiveauthors[8] Chaouadi, R. et al., “Tensile and Fracture Toughness Test Re-sults ofNeutron IrradiatedBeryllium”, ITERTask T23Report(1997).[9] Ferrari, A., Sala, P.R., Fasso, A., and Ranft, J., “FLUKA:a multi-particle transport code”, CERN-2005-10,INFN/TC_05/11, SLAC-R-773 (2005).WEPTY015 Proceedings of IPAC2015, Richmond, VA, USAISBN 978-3-95450-168-73292Copyright©2015CC-BY-3.0andbytherespectiveauthors7: Accelerator TechnologyT20 - Targetry

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Examination of Beryllium under Intense High Energy Proton Beam at CERN's HiRadMat Facility

Examination of Beryllium under Intense High Energy Proton Beam at CERN's HiRadMat Facility

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