Linac Based Based Proton Proton Drivers Linac Thomas P. P. Wangler Wangler Thomas LosAlamos AlamosNational NationalLaboratory Laboratory Los LosAlamos, Alamos,NM NM87544 87544 Los Abstract. overviewis ispresented presentedofofmodern modernhigh-power high-powerproton proton linacs, linacs, including including aa survey Abstract. AnAnoverview survey of of worldwide worldwide applications applicationsthat that are presently underway. The recent trend towards RF superconducting linacs is also discussed. We present some are presently underway. The recent trend towards RF superconducting linacs is also discussed. We present somepreliminary preliminary results from beam-haloexperiment experimentrecently recentlycarried carriedout outatatLos Los Alamos. Alamos. results from thethe beam-halo either coupled-cavity linac linac either aa normal-conducting normal-conducting coupled-cavity (CCL), or SC elliptical cavities for high-velocity (CCL), or SC elliptical cavities for high-velocity particles. is used used throughout throughout the the particles. Magnetic Magnetic focusing focusing is high-velocity section. high-velocity section. INTRODUCTION INTRODUCTION Proton Protonlinacs linacsarearecapable capable ofof producing producing highhighenergy, high-intensity beams with low energy, high-intensity beams with lowemittance. emittance.The The high-intensity performance high-intensity performanceisispossible possiblebecause becausestrong strong focusing cancan bebe easily provided, focusing easily provided,and andbecause becausethe thebeam beam traverses traversesthetheaccelerator acceleratorinina asingle singlepass, pass, avoiding avoiding repetitive repetitiveerror errorconditions conditionsthat that lead lead toto destructive destructive beam resonances as in high-current beam resonances as in high-currentcircular circularmachines. machines. The linac cancanoperate The linac operateatatany anyduty dutyfactor, factor,allallthe theway waytoto 100% duty orora continuous 100% duty a continuouswave wave(CW), (CW),which whichresults results in in acceleration accelerationofofbeams beamswith withhigh highaverage averagecurrent. current.At At present, there present, therearearetwo twomajor majorR&D R&Dtopics topicsininthis thisfield: field: 1) 1)linac linacapplications applicationsofofRF RF superconducting superconducting (SC) (SC) technology, technology,and and2)2)beam beamhalo haloformation formation inin highhighintensity beams.The Thelatter lattertopic topicisismotivated motivatedby bythe the intensity beams. desire control beam lossesand andradioactivation radioactivationofofthe the desire to to control beam losses accelerator,and andthetheneed needforforimproved improvedreliability reliabilityand and accelerator, availability. availability. DC Injector RFQ 50-100 50-100keV keV DTL or IntermediateVelocity Superconducting Structures 2-7 2-7 MeV MeV CCL or Superconducting-Elliptical Structures -100 MeV MeV ~100 ~1GeV GeV ~1 FIGURE of aa modern modern high-power high-powerproton proton FIGURE 1. 1. Block Block diagram diagram of linac. linac. Table for high-power high-power linac linac Table II shows shows the parameters for projects and/or being being constructed. constructed. projects being being designed and/or Included If + and H H"- beams, beams, as as well well Included are are linacs linacs for both H as the IFMIF project that accelerates aa deuteron as the IFMIF project deuteron beam. beam. More details details about about most of these More these linacs linacs are are presented presented other papers papers at this workshop. workshop. Most inin other Most of of these theselinacs linacs would deliver deliver final final beams in the megawatt would megawatt average average beam-power range, range, which qualifies them beam-power them as as highhighpower accelerators. accelerators. Applications Applications include power include linacs linacs for for nuclear-waste transmutation transmutation (KEK/JAERI, nuclear-waste (KEK/JAERI, KOMAC, KOMAC, TRASCO), neutrino neutrino factory factory (CERN TRASCO), (CERN SPL, SPL, FNAL FNAL 8-8GeV), fusion-materials studies (IFMIF), injectors GeV), fusion-materials studies (IFMIF), injectors for for spallation-neutron sources sources (LANSCE, spallation-neutron (LANSCE, SNS, SNS, ESS), ESS),and and proton radiography radiography (LANSCE). (LANSCE). The proton The LANSCE LANSCElinac linacisis the only high-power proton linac that has operated; the only high-power proton linac that has operated; firstbeam beam was was 30 30 years years ago. first ago. ItIt should should be benoted notedthat thatthe the LANSCE linac is the only one that does not have LANSCE linac is the only one that does not have an an RFQ. The SNS, KEK/JAERI, and KOMAC linacs are RFQ. The SNS, KEK/JAERI, and KOMAC linacs are in various stages of construction, and will become the in various stages of construction, and will become the first examples of the modern proton linac architecture first examples of the modern proton linac architecture that was just described. that was just described. Thispaper paperis isdivided dividedinto intotwo twoparts. parts. First, First, we we This presentananoverview overviewofofthe thearchitecture architectureofof modern modern present high-powerproton protonlinacs, linacs, including including a a survey survey ofof high-power worldwide applications that are presently underway, worldwide applications that are presently underway, and we discuss the recent trend toward RF SClinacs. linacs. and we discuss the recent trend toward RF SC Then, we present some preliminary results from the Then, we present some preliminary results from the beam-halo experiment recently carried out at Los beam-halo experiment recently carried out at Los Alamos. Alamos. HIGHPOWER POWERPROTON PROTONLINAC LINAC HIGH OVERVIEW OVERVIEW Figure 1 shows a block diagram of a modern Figure 1 shows a block diagram of a modern proton linac. The first linac accelerating structure is proton The first linac accelerating structure is the linac. radiofrequency quadrupole or RFQ, which thebunches, radiofrequency quadrupole or RFQ, which electrically focuses, and accelerates the beam bunches, electrically focuses, andvelocity accelerates therange beamof from the DC injector to a final in the from the DC injector to a final velocity in the range about β= 0.06 to 0.12. The RFQ is followed byofa about p= 0.06 to 0.12. section The RFQforis acceleration followed by aof magnetically-focused magnetically-focused section for acceleration medium-velocity particles consisting of either ofa medium-velocity particles consisting either or a normal-conducting drift-tube linac of(DTL), normal-conducting drift-tube linacThe (DTL), or “intermediate-velocity” SC cavities. third section, "intermediate-velocity" SC cavities. thirdconsists section,of beginning at a beam velocity of nearThe β=0.5, A new trend during the past decade has been the A new during the past decade hasinbeen interest in trend SC proton linacs. All the linacs Tablethe I interest in SC proton linacs. All the linacs in Table I except for LANSCE and IFMIF have superconducting except foreither LANSCE IFMIFdesign have or superconducting sections in theand baseline as an option. sections either in the during baseline or as an option. Technology progress thedesign past decade, including Technology progress during the past decade, including a large increase in accelerating gradients for SC acavities, large higher increase in input accelerating SC power couplers,gradients and pulsedfor beam cavities, higher power input couplers, and pulsed beam SC electron-linac experience at the TESLA Test SC electron-linac at more the TESLA Facility, has made experience RF SC linacs attractive Test for Facility, has applications. made RF SC linacs more attractive for proton-linac beginning at a beam velocity of near p=0.5, consists of proton-linac applications. CP642, High Intensity and High Brightness Hadron Beams: 20th ICFA Advanced Beam Dynamics Workshop on High Intensity and High Brightness Hadron Beams, edited by W. Chou, Y. Mori, D. Neuffer, and J.-F. Ostiguy 2002 American Institute of Physics 0-7354-0097-0 43 flexibility that that allows allows for for continuing continuing operation operation even even flexibility with the the failure failure of of an an accelerating accelerating module. module.Fourth, Fourth, aa with worldwide industrial industrial capability capability exists exists for for fabrication fabrication worldwide of SC SC cavities cavities and and cryomodules. cryomodules. And And finally, finally, SC SC of cavity performance performance isis still still improving improving with with higher higher cavity accelerating gradients gradients and and higher higher cavity cavity quality quality accelerating factors. The The SNS SNSlinac linacisis scheduled scheduledinin2006 2006totobecome become factors. the first first SC SC proton proton linac, linac, and andits its operation operation will willprovide provide the even more more experience experience for for pulsed pulsed SC SC linac linac operation. operation. even SC There are several significant advantages of SC linacs that account for this trend. First, operating costs costs dissipation. are reduced because of the reduced power dissipation. affordable bore bore Second are the advantages of a larger affordable radius, which relaxes alignment, steering, steering, and and matching tolerances, reduces beam losses losses and and and improves improves beam beam activation, eases commissioning, and with availability. Third, the SC-linac design approach with independently-phased provides short cavities provides TABLE 1. 1. High High Power Power Linac Linac Survey Survey TABLE 1^^^^^ Name Duty IlIlllllillllllllll I'Average Energy Rep •iilllilPiBiiiiiiiiiStart iPulse iiiiiiii iiiiiiiiiHi^^^ factor rate iBiliiii length iiiiiH^ (mA) (mA) (GeV) (MW) date Ion bunch (msec) LANSCE + - H /H (Hz) 0.625 100/20 6.2/1.2 16/9.1 1.0/0.1 1.0 60 6.0 38 - H 2.8 1.2 50 50 14.0 6.0 22 114 ESS Long Pulse H or H+ 2/2.5 16.67 4.2 114/90 FNAL 8 GeV H+/H-/e- 1.0 10 1.0 25 H- 0.5 50/25 2.5 25 1.25 CW CW 100 CW CW 100 CW CW 100 H H CERN SPL lESS llIIIIShort IIHPulse ^ KEK/JAERI 400 MeV - - KEK/JAERI 600 MeV TRASCO IFMIF KOMAC(KAERI) + H D + + - H /H Ave rage (% ) - SNS Average 50 30 0.8 0.8/0.08 ON 1.4 1.0 1.4 2006 1.8 2.2 4.0 ? 3.75 1.33 5+5 2010 0.25 8.0 2.0 ? 0.7 0.4 0.35 0.6 0.21 ? 30 >1.0 >30 ? 0.040 10.0 2010 2X125 2X125 20 20 0.28/0.14 2006 0.1(1.0) 2.0(20) 2011(?) component component was was aa unique unique transverse transverse beam beam profile profile 8 scanner scanner8 consisting consisting of of aa thin, thin, 33 33 µ|i diameter, diameter, carbon carbon wire wire for for measurement measurement of of the the dense dense beam beam core, core, and and aa pair pair of of 1.5-mm 1.5-mm thick thick scraper scraper plates plates totoprovide providegreater greater sensitivity sensitivity for for measurement measurement of of the the outer outer halo halo regions. regions. Each wire and its associated pair of scraper Each wire and its associated pair of scraper plates plateswere were mounted mounted on on aa common common movable movableframe. frame. As Asthe theprotons protons passed passed through through the the wire wire aa signal signal was was induced induced from from secondary secondary electron electron emission. emission. The The scraper scraper plates plates were were water-cooled water-cooled and and were were constructed constructed of of graphite graphitebrazed brazed onto onto copper. copper. A A signal signal was was induced induced by by the the beam beam protons protons that that stopped stopped in in the the plates. plates. The The data data from from the the wires wires and and the the plates plates were were combined combined using using computer computer software with software to to produce produce aa single single distribution distribution with aa 55 dynamic intensity range of about 10 :1. dynamic intensity range of about 10 :1. Nine Nine measurement measurement stations, stations, shown shown in in Fig. Fig. 2,2, were were located located midway midway between between pairs pairs of ofquadrupoles; quadrupoles;atateach eachlocation location both both the the horizontal horizontal and and vertical vertical projected projected distributions distributions were were measured. measured. The The first first station station was was located located after after quadrupole 4. The next four stations were located quadrupole 4. The next four stations were locatedafter after the the beam beam had had debunched debunched at at quadrupoles quadrupoles 20, 20, 22, 22, 24, 24, and and 26. 26. The The last last four four stations stations were were located located after after quadrupoles quadrupoles 45, 45, 47, 47, 49, 49, and and51. 51. LOS ALAMOS BEAM BEAM HALO HALO EXPERIMENT Theoretical Theoretical research research during during the the past past decade decade has has led led to aa picture picture of to of space-charge space-charge forces forces in in mismatched mismatched beams as beams as aa major major source source of of beam beam halo halo in in high-current high-current proton beams. proton beams. The The nonlinear nonlinear space-charge space-charge force force experienced by experienced by individual individual particles, particles, while while the the beam beam is is undergoing coherent undergoing coherent rms-size rms-size oscillations, oscillations, slowly slowly drives some drives some particles particles to to larger larger amplitudes amplitudes to to form form aa halo. The mechanism has been described by a particlehalo. The mechanism has been described by a particle1,2,3 1 2 3 and identified as a parametric core model, core model, ' ' and identified as a parametric resonance. 22 resonance. An experiment been carried An experiment has has been carried out out at at Los Los Alamos Alamos to test test these to these ideas. ideas. A A 52-quadrupole 52-quadrupole FODO FODO beambeamtransport channel transport channel was was installed installed at at the the end end of of the the LowLowEnergy Demonstration Energy Demonstration Accelerator Accelerator (LEDA) (LEDA) 6.7-MeV, 6.7-MeV, CW, CW, 350-MHz 350-MHz RFQ RFQ to to carry carry out out aa first first experimental experimental 4,5,6 study of beam-halo formation in a study of beam-halo formation in a proton proton beam. beam.4'5'6 The channel The channel was was long long enough enough for for the the development development of of about 10 mismatch oscillations, enough about 10 mismatch oscillations, enough to to observe observe the the initial stages initial stages of of emittance emittance growth growth and and halo halo formation formation caused by compliment of caused by mismatch. mismatch. A A large large compliment of beam beam 7 7 The key diagnostic diagnostics was provided. diagnostics was provided. The key diagnostic 44 RFQ 44 RFQ 20-26 20-26 pure pure breathing-mode breathing-mode mismatch. mismatch. The The mismatch mismatch strength was measured by a parameter µ, strength was measured by a parameter |i,which whichequals equals the beam theratio ratioofofthe therms rmssize sizeofofthe theinitial initialmismatched mismatched beam totothat thatofofthe thematched matchedbeam. beam. 45-51 45-51 The 1 Hz Thebeam beamfrom fromthe theion ionsource sourcewas waspulsed pulsedat at 1 Hz totoallow the use of interceptive beam diagnostics. The allow the use of interceptive beam diagnostics. The measurement cycle consisted of the following steps. measurement cycle consisted of the following steps. The CW RFQ was de-energized with an RF blanking The CW RFQ was de-energized with an RF blanking pulse, when the ion source was turned on. While the pulse, when the ion source was turned on. While the 75-keV dc-injector beam current increased, the beam 75-keV de-injector beam current increased, the beam was injected into the unpowered RFQ. After about 2 was injected into the unpowered RFQ. After about 2 msec, the RF blanking pulse was removed; the RFQ msec, the RF blanking pulse was removed; the RFQ fields approached a steady state after another 5 µsec. fields after on another 5 (isec. The ionapproached source and aRFsteady fields state remained for another The ion source and RF fields remained on for another 30 µs for data acquisition. The beam-profile 30 (is forweredata The beam-profile diagnostics all acquisition. in a fixed position during a diagnostics were all in a fixed position measurement, and only one wire or scraper wasduring in the a measurement, and only one wire or scraper was beam at a time; all other wires and scrapers were in outthe at a time; aperture. all other wires andorscrapers ofbeam the beam-pipe The wire scraper were in theout of theaccumulated beam-pipe beam-induced aperture. The charge wire orover scraper beam aboutin30the beam Only accumulated beam-induced charge over10about µsec. the charge collected over the last µsec,30 (isec.the Only thehad charge over the last 10 (isec, when beam best collected approximated a steady state, whenselected the beam approximated a steady state, was for had thebest recorded data. Then the DC was selected for the recorded data. Then the DC injector was turned off, and the beam profile scanners FIGURE 2. Block diagram of the 52 quadrupole transport FIGURE 2. Block diagram of the 52 quadrupole transport channel showing the locations of the 9 profile scanners. channel showing the locations of the 9 profile scanners. Beam matching was done by adjusting the first four Beam matching was done by adjusting the first four quadrupoles to produce equal rms sizes in both x and quadrupoles to produce equal rms sizes in both x and y. We estimated a measurement uncertainty for the y. We estimated a measurement uncertainty for the rms beam sizes about 50µ, caused mostly by rms beam sizes mostly by transverse beam about jitter. 50|i, A caused least-squares-fitting transverse beam jitter. A least-squares-fitting procedure was used based on measurements of procedure usedsizes based measurements of derivatives was of rms withonrespect to the four derivatives of rms sizes with respect to the four matching quadrupole gradients. The Courant-Snyder matching gradients. parametersquadrupole of the matched beamThe canCourant-Snyder be calculated parameters of the matched beam can be calculated from the beam dynamics using the measured values of from the beamrms dynamics usingPure the measured values of the matched beam sizes. mode mismatches the matched rms beam sizes. Pure mismatches were calculated by scaling the mode Courant-Snyder were calculated scaling the and Courant-Snyder parameters to the bydesired values finding the parameters to the desiredquadrupoles values andthatfinding the settings of the matching produced settings of the matching quadrupoles that produced these values. For example, multiplying each of the these values. For example, multiplying each of αthe four transverse Courant-Snyder ellipse parameters x, four transverse Courant-Snyder ellipse parameters βx, αy, and βy by the same scaling factor producedOx, a injector was turned off, and the beam profile scanners px, Oy, and py by the same scaling factor produced a Combined X Dlstn button Combined X Dlstn button 0 A 0 1 o \ S- 10 V ~ f"0> "S ^ / 10 M H « ——— 1 10-10 -20 -10 0 10 20 - 1 5 - 1 0 PosFtlon (mm) 5 10 15 Combined X Dlstn button Combined X Dlstn button ^ 5 0 Position (mm) 10^ niiurF" T&iiin.. i TflfttH^ jflfifir /\ -H^ i 1 Qn ~l~ 1 10~ 2 _i_ 10~ + 10 -a - 1 5 - 1 0 - 5 0 5 - 1 5 - 1 0 - 5 0 5 10 FIGURE 3. Measured beamPosition profiles {mm} in x at 75 mA: (upper left) scanner 22, µ=1.0, matched,;(upper right) scanner 22, µ=1.5 Poaftlon (mm) mismatched,;(lower left) scanner 51, µ=1.0 matched,;(lower right) scanner 51, µ=1.5 mismatched. 10 15 15 FIGURE 3. Measured beam profiles in x at 75 mA: (upper left) scanner 22, u=1.0, matched,;(upper right) scanner 22, u=1.5 mismatched,;(lower left) scanner 51, ji=1.0 matched,;(lower right) scanner 51, (1=1.5 mismatched. 45 were cycle. were repositioned repositioned for for the the next next cycle. were repositioned for the next cycle. Among to characterize characterize the the beam beam Among the the methods methods used used to Among the methods usedand to characterize the beamat were: 1) the rms emittance, 2) the beam widths were: 1) the rms emittance, and 2) the beam widths at were: 1) the rms emittance, andpeak 2) the intensity. beam widths at different Rms different fractions fractions of of the the peak intensity. Rms different fractions of the peak intensity. Rms emittances 45 were were calculated calculated from from emittances at at scanners scanners 20 20 and and 45 at scanners 20 andusing 45 were calculated from aaemittances least-squares procedure rms measurements procedure using rms measurements a least-squares least-squares procedure using rms measurements from the profiles at the four scanners in each each cluster. from the profiles at the the four four scanners scanners in cluster. from the profiles at in each cluster. Analysis of of the the rms-emittance rms-emittance data data for for comparison comparison Analysis Analysis of the rms-emittance data for in comparison with free-energy theory is now progress. with free-energy theory is now in progress. with free-energy theory is now inmismatches progress.at Preliminary results for breathing-mode Preliminary results for breathing-mode mismatches at Preliminary results for breathing-mode mismatches 75 mA mA suggest suggest rapid rate of of emittance emittance growth that thatatis is 75 aa rapid rate growth 75 mA suggest a rapid rate of emittancetransfer growth of thatfree is consistent with a large fractional consistent with a large fractional transfer of free consistent with a energy large fractional of free energy to to thermal thermal within only onlytransfer few mismatch mismatch energy energywithin within aafew few energy to thermal energy only a mismatch oscillations. oscillations. oscillations. Initial multiparticle multiparticle simulation simulation work work has has resulted resulted in in Initial Initial multiparticle simulation workgrowth has resulted in smaller beam widths and emittance rates for smaller beam beam widths widths and and emittancegrowth growthrates ratesfor for smaller the mismatched mismatched beams emittance than are are experimentally experimentally the beams than the mismatched beamsthe than observed. However, inputare6D 6Dexperimentally phase space space observed. However, the input input phase observed. However, the 6D phase space distribution was not measured in the experiment. distribution was was not not measured measured inin the the experiment. experiment. distribution Simulations of of the the experiment experiment using using different different possible Simulations possible Simulations of the experiment using different possible input distributions show that the input distributions input distributions distributions show show that that the the input input distributions distributions input with more more extended extended tails tails generate generate more emittance emittance with more with moreGood extended tails generate more emittance growth. agreement between experiment and growth. Good Good agreement agreement between between experiment experiment and and growth. simulation may require detailed knowledge of the simulation may may require detailed detailed knowledge knowledge ofof the the simulation initial transverse transverserequire phase-space distributions, distributions, especially especially initial phase-space initial phase-space distributions, especially for the thetransverse tails. for tails. for the tails. PRELIMINARY RESULTS FOR 75 75 MA MA PRELIMINARY RESULTS FOR FOR PRELIMINARY RESULTS 75 MA Measurements were made at 16, 16, 50, 50, 75, 75, and and 100 100 Measurements were made made at at Measurements were 16, 50, 75, µ. andIn 100 mA and for a range of mismatch parameters, this mA for aa range range of of mismatch mismatch parameters, parameters, |i. µ. In In this this mA and andwefor paper report preliminary results at 75 mA. The paper report preliminary results results at at 75 75 mA. mA. The The paper we we transverse report preliminary measured profiles for the the matched matched beams measured transverse profiles for beams measured transverse profiles profiles in forthe the linear matched beams have Gaussian-like plots (not have Gaussian-like profiles in in the the linear linear plots plots (not have Gaussian-like profiles (not shown). The semilog plots for the matched beams (see shown). The semilog plots for for the the matched matched beams beams (see shown). The evidence semilog plots Fig. 3) show of an extended low-density (see halo Fig. 3) show evidence of an extended low-density halo Fig. may 3) show evidenceinofthe an input extended low-density halo that be present beam. The measured that be present present in in the the input input beam. beam. The measured measured that may may be transverse profiles for the mismatchedThe beams show show transverse profiles for for the the mismatched mismatched beams transverse profiles beams show (see Fig. 3) structure in the form of of shoulders shoulders in in the (see Fig. 3) structure in the form the -3 (see Fig.plots, 3) structure in the form of shoulders in 10 the semilog and some asymmetric profiles at semilog plots, and some asymmetric asymmetric profiles profiles at at 10" 103-3 semilog plots, and some level. Figures 44 and show the xx and and yy rms rms sizes sizes at at the the level. and 555 show show the the level. Figures Figures 4 and x and and mismatched y rms sizes atcase, the different scanners for a matched different for aa matched matched and and mismatched mismatched case, case, different scanners scanners for respectively. respectively. respectively. SUMMARY SUMMARY SUMMARY Proton linacs linacs are are capable capable of producing producing highhighProton Proton linacs are capable ofof producing highenergy, high-intensity beams with low emittance. At energy, high-intensity high-intensity beams beams with with low lowemittance. emittance.At At energy, present, there are two major R&D topics in the proton present,there thereare aretwo twomajor majorR&D R&Dtopics topicsininthe theproton proton present, linear accelerator accelerator field: field: 1) 1) linac linac applications applications of RF RF SC SC linear linear accelerator field: 1) linac applications ofofRF SC technology, and 2) beam halo formation in hightechnology, and and 2) 2) beam beam halo halo formation formation inin highhightechnology, intensity beams. beams. A new new trend trend during during the the past past decade decade intensity intensity beams. AA new trend during the past decade has been been the the growing growing interest interest in in SC SC proton proton linacs, linacs, has has been the growing interest in SC proton linacs, resulting from advantages for reduced operating costs, resulting from fromadvantages advantagesfor forreduced reducedoperating operatingcosts, costs, resulting larger bore radius, greater operating flexibility, and larger bore bore radius, radius, greater greater operating operating flexibility, flexibility, and and larger reduced capital costs as accelerating gradients reduced capital capital costs costs asas accelerating accelerating gradients gradients reduced continuetoto toincrease. increase.AA Abeam beamhalo haloexperiment experimenthas hasbeen been continue increase. beam halo experiment has been continue carried out at Los Alamos, and analysis of the data is carried out out atatLos LosAlamos, Alamos,and andanalysis analysisofofthe thedata dataisis carried now in progress. Analysis of the rms-emittance data now inin progress. progress. Analysis Analysis ofofthe therms-emittance rms-emittancedata data now for comparison comparison with with free-energy free-energytheory theoryisis isnow nowinin in for comparison with free-energy theory now for progress. Preliminary results for breathing-mode progress. Preliminary Preliminary results results for for breathing-mode breathing-mode progress. mismatches atat at 75 75 mA mA suggest suggest aaa rapid rapid rate rate ofof of mismatches 75 mA suggest rapid rate mismatches emittance growth that is consistent with a large emittance growth that is consistent with a large emittance growth that is consistent with a large fractional transfer transfer ofof of free free energy energytoto tothermal thermalenergy energy fractional transfer free energy thermal energy fractional withinonly onlyfew fewmismatch mismatchoscillations. oscillations. within only few mismatch oscillations. within 2.5 2.5 Rmssize(mm) size(mm) Rms 2.0 2.0 1.5 1.5 1.0 1.0 0.5 0.5 xrms xrms yrms yrms 0.0 0.0 17 17 17 22 22 22 27 27 27 32 32 37 37 37 Scanner Scanner 42 42 42 47 47 47 52 52 FIGURE displacements at 888 profile profile scanners scanners for for FIGURE 4. 4. Rms displacements at at profile scanners for Rms displacements matched beam case (µ=1.0) at 75 mA. matched beam case (µ=1.0) 75 mA. mA. (|i=1.0) at 75 2.5 2.5 Rmssize size(mm) (mm) Rms 2.0 2.0 ACKNOWLEDGMENTS ACKNOWLEDGMENTS ACKNOWLEDGMENTS 1.5 1.5 Thankstoto toR. R.Garoby, Garoby,J.J. J.M. M.Lagniel, Lagniel,R.R. R.Ferdinand, Ferdinand, Thanks Thanks R. Garoby, M. Lagniel, Ferdinand, I. Masanori, Masanori, C. Pagani, J. Wei, W. Park, and others I.I. C. Pagani, J. Wei, W. Park, and Masanori, C. Pagani, J. Wei, W. Park, andothers others who provided input or help for the high-power linac who provided input or help for the high-power linac who provided input or help for the high-power linac survey presented presented inin in Table Table 1.1. 1. I II wish wishtoto tothank thankIngo Ingo survey survey presented Table wish thank Ingo Hofmann for for sending sending usus us aaa draft draft ofof ofhis hispaper paperonon on Hoftnann Hofmann for sending draft his paper anisotropyeffects effectsinin inmismatched mismatchedbeams, beams,which whichisis isvery very anisotropy anisotropy effects mismatched beams, which very helpfulfor forinterpreting interpretingour ourexperimental experimentalresults. results.I IIalso also helpful helpful for interpreting our experimental results. also want toto to acknowledge acknowledge the the contributions contributions ofof of my my want want acknowledge the contributions my colleagues on the beam-halo experiment team, colleagues colleagues on on the the beam-halo beam-halo experiment experiment team, team, particularlyC. C.K. K.Alien, Allen,K. K.C. C.D. D.Chan, Chan,P.P. P.Colestock, Colestock, particularly particularly C. K. Allen, K. C. D. Chan, Colestock, 1.0 1.0 I i.o0.5 0.5 xrms xrms yrms yrms 0.0 0.0 17 17 22 22 27 27 32 32 37 37 37 42 42 47 47 52 52 Scanner Scanner Scanner FIGURE displacements at 88 profile profile scanners scanners for for FIGURE 5. 5. Rms Rms displacements displacements at profile scanners for the mismatch case (|i=1.5) (µ=1.5) at at 75 75mA. mA. the breathing breathing mode mismatch mismatch case case (µ=1.5) at 75 mA. 46 K. R. Crandall, R. W. Garnett, J. D. Gilpatrick, W. Lysenko, J. Qiang, J. D. Schneider, M. E. Schulze, R. Sheffield, and H. V. Smith for the work that was described in this paper. REFERENCES 1. J.S. O'Connell, T.P.Wangler, R.S.Mills, and K.R.Crandall, Proc. of 1993 Part. Accel. Conf., IEEE Catalog No. CH3279-7, 3657-3659. 2. R.L. Gluckstern, Phys. Rev.Lett. 73, 1247 (1994). 3. For an overview, see T.P.Wangler, K.R.Crandall, R.Ryne, and T.S.Wang, Phys.Rev. ST Accel. Beams I (084201)1998. 4. P.L.Colestock, et.al, "Measurements of Halo Generation for a Proton Beam in a FODO Channel," Proc. 2001 Part. Accel. Conf., IEEE Catalog No. 01CH37268, 170-172. 5. Martin Schulze, et al, "Characterization of the Proton Beam from the 6.7 MeV LEDA RFQ," Proc. 2001 Part. Accel., IEEE Catalog No. 01CH37268, 591-593. 6. T.P.Wangler, et al., Experimental Study of Proton-Beam Halo Induced by Beam Mismatch in LEDA," Proc. 2001 Part. Accel., IEEE Catalog No. 01CH37268, 2923-2925. 7. J.D.Gilpatrick, et al., "Experience with the Low Energy Demonstration Accelerator (LEDA) Halo Experiment Beam Instrumentation," Proc. 2001 Part. Accel., IEEE Catalog No. 01CH37268, 2311-2313. 8. J.D.Gilpatrick, et al., "Beam-Profile Instrumentation for Beam Halo Experiment: Overall Description and Operation," Proc. 2001 Part. Accel., IEEE Catalog No. 01CH37268, 525-527. 47
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