1. 6 th International Conference on Nuclear Physics at Storage Rings 23-26 May 2005, Jülich - Bonn, Germany ÖRJAN NORDHAGE GSI/Uppsala University Germany/Sweden A high-density pellet target for antiproton physics with

2. May 25, 2005Örjan Nordhage, STORI'052 Contents 1.PANDA – Motivation 2.Pellet Target – Principle, WASA, Target Thickness, Requirements, R&D, Pellet Tracking 3.Implementation into PANDA 4.Conclusion

3. May 25, 2005Örjan Nordhage, STORI'053 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

4. May 25, 2005Örjan Nordhage, STORI'054 Target thickness at or HESR Number of antiprotons: 1×10 11 Momentum range: 1.5 – 15 GeV/c (β: 0.848 – 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

5. May 25, 2005Örjan Nordhage, STORI'055 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)]

6. May 25, 2005Örjan Nordhage, STORI'056 WASA Pellet Target – Principle Freeze either in v.i.c. or within some cm after 70-100 kHz 5-10,000 /s Completely frozen: bounce like billiard balls [To be printed, NIM A (2005)] What gets through is very close to homogenously distributed

7. May 25, 2005Örjan Nordhage, STORI'057 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

8. May 25, 2005Örjan Nordhage, STORI'058 Target thickness and pellets Pellets are discrete and locally very thick ~ 10 19 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)

9. May 25, 2005Örjan Nordhage, STORI'059 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

10. May 25, 2005Örjan Nordhage, STORI'0510 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)

11. May 25, 2005Örjan Nordhage, STORI'0511 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

12. May 25, 2005Örjan Nordhage, STORI'0512 R&D: PTS vacuum measurement [Technical Progress Report for PANDA (2005)] Input to VAKLOOP [SLAC-PUB-5962]  PTS Geometry  Corresponding conductance  Pellet outgassing [To be printed, NIM A (2005)]  Pumping speed

13. May 25, 2005Örjan Nordhage, STORI'0513 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

14. May 25, 2005Örjan Nordhage, STORI'0514 Pellet Target in the -detector 3.7m (Corresponding distance for WASA: 3.3m)

15. May 25, 2005Örjan Nordhage, STORI'0515 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 N.B. 12.5m in z-direction

16. May 25, 2005Örjan Nordhage, STORI'0516 Thanks to… Hans Calén, Curt Ekström, Carl-Johan Fridén, Zhankui Li, Gunnar Norman Florian Lang, Inti Lehmann, Matthias Schult, Ulrich Wiedner Present and recent pellet collaborators: Funding: EU, GSI, Swedish Research Council Uppsala (ISV): TSL:

17. May 25, 2005Örjan Nordhage, STORI'0517 Conclusion  To reach the design luminosity in PANDA, a Pellet Target might be the only possible 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 is going to be used for further tests  The vacuum condition has been experimentally tested – agrees with calculations  A Pellet Tracking System is an excellent approach to the (close to perfect) vertex determination

18. May 25, 2005Örjan Nordhage, STORI'0518 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. Plot is independent of pellet speed