ÖRJAN NORDHAGE GSI/Uppsala University Germany/Sweden A high-density pellet target for antiproton physics with 2 nd Swedish Workshop on FAIR Physics, Lund, September 12-13, 2005

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting2 Contents 1.PANDA – Motivation 2.Pellet Target – Principle, WASA, Target Thickness, Requirements, R&D, Pellet Tracking 3.Implementation into PANDA 4.Conclusion (For details, please see the proceedings of STORI’05)

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting3 Motivation for Physics program: Charmonium spectroscopy (mass, width, decay branches) Gluonic excitations (charmed hybrids, glueballs) Properties of charmed mesons in nuclei Single and double hypernuclei spectroscopy … Very rare events together with a limited number of antiprotons, put high demands on the target and its thickness

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting4 Target thickness at or HESR Number of antiprotons: 1×10 11 Momentum range: 1.5 – 15 GeV/c (β: – 0.998) HESR circumference: 574 m Design luminosity: 2×10 32 cm -2 s -1 The reaction pp means a pure hydrogen target and currently, pellets (frozen micro-spheres) are the only proven working solution, which provides such an effective target thickness

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting5 Pellet Target – Principle Pellet generation: 1)Cooling of gas to liquid 2)Jet break-up into droplets 3)Vacuum injection 4)Skimmer to collimate the pellet beam [B. Trostell, NIM A 362 (1995) and/or C. Ekström et al., NIM A 371 (1996)]

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting6 WASA Pellet Target – Principle Freeze either in v.i.c. or within some cm after kHz 5-10,000 /s Completely frozen: bounce like billiard balls [Ö.N. et al., NIM A 546 (2005)] What gets through is very close to homogenously distributed

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting7 WASA Pellet Target – Dimensions Vac. inj. cap. exit: 0 m Skimmer (Φ=0.59mm): 0.7 m Interaction point: 2.4 m Dump: 3.6 m Bounce at skimmer Get through skimmer Define pellet spread at i.p., we get N.B. Target geometry (skimmer position and diameter Φ) alone define S ip

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting8 Target thickness and pellets Pellets are discrete and locally very thick ~ atoms/cm 2 Thus, the effective thickness needs an associated area Pellet beam ‹l›‹l› Antiproton beam S ip Maximum luminosity if beam area and target area are matched N.B. Not in scale: beam (~mm) >> pellet (~30μm)

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting9 Pellet requirements at or HESR With we need pellets of a certain size, and how often? Last H 2 run (Dec. 2003): f~9000/s, 33μm, 95m/s A factor less than 2 off from is already achieved R&D

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting10 R&D of Pellet Parameters – How To Goal: smaller pellets much more often Size reduction by: 1)Decreased nozzle outlet 2)Increased transducer frequency 3)Decreased driving pressure Rate increase by: 1)Improved survival ratio 2)Decreased angular spread Spread due to transverse velocity component of gas after the v.i.c.? If so, simulations by FEMLAB might give us the ideal geometry (of the exit)

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting11 R&D of Pellet Parameters – Location Pellet Test Station (PTS) at The Svedberg Laboratory (TSL) Pellet pipes ”antiproton beam pipe” Vacuum gauges Upper floor Lower floor in Uppsala:

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting12 R&D: PTS vacuum measurement [Technical Progress Report for PANDA (2005)] Input to V. Ziemann’s VAKLOOP [SLAC-PUB-5962]  PTS Geometry  Corresponding conductance  Pellet outgassing [Ö.N. et al., NIM A 546 (2005)]  Pumping speed

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting13 CELSIUS/WASA interaction region: R&D: Beam-caused pellet heating The mass loss of pellets is temperature dependent The beam will deposit energy to the pellets Thus: an increase in pellet temperature and mass loss Question: Vacuum effect? Answer from (!?!): ”Dedicated Spring’05 experiment at CELSIUS” 48 MeV protons Pellets Gauge

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting14 R&D: Beam-caused pellet heating Current in green [0,2] mA, pressure in red [1.3,2.5]×10 -7 mbar Measured beam size:Ultimately, the goal is to evaluate this additional effect for PANDA – just wait until later this Autumn Time [s]

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting15 R&D: Pellet Tracking/Profile System Basic idea:Sofar existing (1D): LineScanCam, 512 pixels, readout 98 kHz (+laser, framegrabber) Pellets’ discrete nature is an advantage – allows for a localized target and a well-defined vertex Goal: combined pellet counter and profile system – online

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting16 Pellet Target in the -detector 3.7m (Corresponding distance for WASA: 3.3m)

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting17 N.B. 12.5m in z-direction Pellet Target in the -detector HESR-vacuum distribution for two different pellet sizes, but the same target thickness Define: ’background due to gas to signal from pellet’-ratio

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting18 Thanks to… Hans Calén, Curt Ekström, Carl-Johan Fridén, Zhankui Li, Gunnar Norman Florian Lang, Inti Lehmann, Jonas Lith, Matthias Schult, Ulrich Wiedner Present and recent pellet collaborators: Funding: EU, GSI, Swedish Research Council Uppsala (ISV): TSL:

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting19 Conclusion  To reach the design luminosity in PANDA, a Pellet Target is a very promising option due to the high target thickness it provides  The existing WASA Pellet Target is almost suitable as it is – and we know how to improve it further  The Pellet Test Station at TSL is going to be used for further tests  The vacuum condition has been experimentally tested – agrees with calculations (results on beam- pellet interaction is being analyzed now…)  A Pellet Tracking System is an excellent approach to the (close to perfect) vertex determination Thanks for your attention!

Sept. 12, 2005Örjan Nordhage, 2nd SFAIR meeting20 Pellet requirements at or HESR The pellet size goal is determined by the inter- pellet distance that could be matched by the antiproton beam N.B. The plot is independent of pellet speed