We test a target concept devised for the purpose of producing copious secondary pions and capturing the muon decay products. This experiment is designed to test the target system for a neutrino factory or muon collider and consists of a free flowing mercury stream embedded in a high-field solenoid. Key components are described

Carroll, A.

Efthymiopoulos, I.

Fabich, A.

Haug, F.

Kirk, H. G.

Lettry, J.

Mokhov, N. V.

Palm, M.

Park, H. J.

Striganov, S.

Tsang, T.

UNT Digital Library

A HIGH-POWER TARGET EXPERIMENT AT THE CERN PSH.G Kirk∗, H.-J. Park, T. Tsang, BNL, Upton, NY 11973, USAA. Fabich, I. Efthymiopoulos, F. Haug, J. Lettry, M. Palm,CERN, CH-1211 Gene`ve 23, SwitzerlandN. Mokhov, S. Striganov, FNAL, Batavia, IL, 60510, USAA. Carroll, V.B. Graves, P.T. Spampinato, ORNL, Oak Ridge, TN 37831, USAK.T. McDonald, Princeton University, Princeton, NJ 08544, USAJ.R.J. Bennett, O. Cannetta, P. Loveridge, CCLRC, RAL, Chilton, OX11 0QX, UKAbstractWe test a target concept devised for the purpose of pro-ducing copious secondary pions and capturing the muondecay products. This experiment is designed to test thetarget system for a neutrino factory or muon collider andconsists of a free flowing mercury stream embedded in ahigh-field solenoid. Key components are described.INTRODUCTIONThe U.S. Neutrino Factory and Muon Collider Collab-oration (refereed to here after as the Muon Collaboration)has been pursuing a solution to generate an intense muonbeam suitable for pursuing advanced physics experimentsbased on circulating muon beams in storage rings. In thecase of a Muon Collider this goal is realized through collid-ing, counter-circulating muon beams. For a Neutrino Fac-tory, intense neutrino beams can be generated through thedecay of circulating muon beams in suitably placed longstraight sections.A key component of this program is establishing thetechnology to generate a copious source of muons. A pro-posed solution [1, 2] consists of converting a powerful pri-mary proton beam into an intense pion beam. These pionsare then conducted into a decay channel where the muondecay products can be collected. Primary proton beamswith megawatt class power are being considered, in partic-ular, for a Neutrino Factory, 4-MW proton beam power isthe baseline option.Designing a target system capable of handling suchbeam power is a challenging endeavor. Consequently, theMuon Collaboration has embarked on an R&D programwith the goal to develop and demonstrate the required tech-nology.THE TARGET CONCEPTThe basic concept for muon production consists of utiliz-ing a high-Z target which will generate copious low-energypions of both signs and then capturing them within the con-fines of an high field solenoid. The proposed target material∗ hkirk@bnl.govlength cm               radiicmPPPHg PoolSC CoilsFe Cu CoilsHg ContainmentBe WindowFigure 1: Concept of a continuous mercury jet target foran intense proton beam. The jet and beam are tilted by100 mrad and 67 mrad, respectively, with respect to a 20-Tsolenoid magnet that conducts low-momentum pions into adecay channel.is a liquid mercury jet which can easily be replenished af-ter each interaction with the proton beam. Solenoid fieldsof 15-20 T will be adequate to capture most pions with P⊥up to 220 MeV/c. These pions are then conducted alonga tapered solenoid channel in which the muon decay prod-ucts of the pions are contained and further transported intophase space shaping systems such as phase rotation in lon-MOPAS094 Proceedings of PAC07, Albuquerque, New Mexico, USA07 Accelerator Technology Main Systems646T28 Subsystems, Technology and Components, Other1-4244-0917-9/07/$25.00 c©2007 IEEEFERMILAB-CONF-07-593-APCgitudinal phase space and cooling channels in which thetransverse emittance of the muons is reduced. Figures 1aand b show the schematics of the capture scheme. Figure2 gives a view of the infrastructure required to support atarget system of this type.Figure 2: Concept of the target vault for a 4-MW mercuryjet target [3].There are key technical issues associated with this pro-posed targeting solution. The performance of the mercuryjet will be effected by the presence of the magnetic field.The dispersal of the mercury after the interaction with theproton beam needs to be studied. Other issues include howmuch displaced in time can micro-bunches be and still havefull pion production and the corollary question, how sooncan the jet be reconstituted in order to accept a subsequentbeam pulse. These and other issues represent the basis forthe Muon Collaboration establishing its targetry R&D pro-gram.THE TARGET EXPERIMENTInitial experiments were conducted at the BNL AGS [4]in which the characteristics of the interaction of an Hg jetwith a 24-GeV proton beam was first studied. These stud-ies gave encouraging but limited results. First, the Hg jetvelocity was only 2.5 m/s, whereas one of order 20 m/sis required for high rep. rate (≈ 50-Hz) operations. Also,the previous experiments did not include the presence of amagnetic field. With this in mind, a proposal [5] was sub-mitted and subsequently accepted for testing at CERN us-ing the 24-GeV proton beam from the CERN PS. An initialdiscussion of the concept for this experiment has alreadybeen published [6].Two key experimental components of this experiment,the 15-T Pulsed solenoid and the Hg injection system, havebeen described elsewhere [7, 8]. The experimental floorlayout of these systems are shown in Fig. 3 while the re-lationship of the equipment relative to the proton beam isshown in Fig. 4.The beam spill will be varied with single turn extractionused for the 24-GeV PS proton beam. Beam pulses willFigure 3: Layout of the high-power-target experiment.Figure 4: Cutaway view of the high-power-target experi-ment.vary in intensity from 4 to 30 × 1012 protons/pulse (4-30TP). Multiple turn extractions can be realized provided thatthe primary proton beam energy is reduced to 14 GeV. Thetime interval between the extractions can be varied from2 to 500 µs. We will exploit this machine capability byinvoking a pump-probe technique to examine the particleproduction efficiency of the trailing (probe) pulse as a func-tion of the time interval. This will give more detailed infor-mation concerning cavitation development in the mercuryjet.The particle production efficiencies of each micro-pulsewill be examined through the use of various particle detec-tors arrayed about the interaction site. Two types of de-tectors will be used: diamond based PIN-diode and Alu-minum Cathode Electron Multipliers (ACEM). We use theparticle production code MARS as a guide to predict theexpected particle fluences and time distributions at selectedlocations, as shown in Fig. 5.CONCLUSIONSThe CERN target experiment is structured to provide aproof-of-principle verification of the Muon Collaborationtarget concept. Principle components have been installedand the running of the experiment is expected to begin thissummer.ACKNOWLEDGMENTSThis work was supported in part by the US DOE Con-tract NO. DE-AC02-98CH10886.Proceedings of PAC07, Albuquerque, New Mexico, USA MOPAS09407 Accelerator Technology Main Systems1-4244-0917-9/07/$25.00 c©2007 IEEET28 Subsystems, Technology and Components, Other647Figure 5: Secondary pion fluxes for a pulse of 3 × 101324-GeV protons on an Hg target, shown in the horizontalplane at beam height, according to the MARS code. Thepositions of 12 particle detectors are indicated in the figure.REFERENCES[1] H.G. Kirk, Targetry for a µ+µ− Collider, Proc. 1999 Part.Accel. Conf., p. 3030.[2] K.T. McDonald et al., The Primary Target Facility for a Neu-trino Factory Based on Muon Beams, Proc. 2001 Part. Accel.Conf., p. 1583.[3] P. Spampinato, et al., Target Enclosure and System Designfor a Mercury-Target Neutrino Producing Facility, Proc. 2005Part. Accel. Conf., p. 1580.[4] H.G. Kirk, et al., Target Studies with BNL E951 at the AGS,Proc. 2001 Part. Accel. Conf., p. 1535.[5] J.R.J. Bennett, et al., Studies of a Target System for a 4-MW,24 GeV Proton Beam, Proposal to the CERN INTC Commit-tee, INTC-P-186 (April 26, 2004),http://puhep1.princeton.edu/mumu/target/cern proposal.pdf[6] H.G. Kirk, et al., A High-Power Target Experiment, Proc.2005 Part. Accel. Conf., p. 3745.[7] H.G. Kirk, et al., A High-field Pulsed Solenoid for LiquidMetal Target Studies, Proc. 2003 Part. Accel. Conf., p. 1631.[8] V.B. Graves, et al., Systems Testing of a Free Hg Jet Systemfor Use in a High-Power Target Experiment, these Proceed-ings.MOPAS094 Proceedings of PAC07, Albuquerque, New Mexico, USA07 Accelerator Technology Main Systems648T28 Subsystems, Technology and Components, Other1-4244-0917-9/07/$25.00 c©2007 IEEE

A high-power target experiment at the CERN PS

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A high-power target experiment at the CERN PS

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