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					    Moscow-Jülich Pellet Target




                                                    … a brief status report
Markus Büscher   PANDA collaboration meeting, Dubna, 04/07/2007               1
    INTAS project

     • “Development of a Pellet Target for PANDA”
                     (INTAS 06-1000012-8787, 2007/08)


     • Consortium:
         FZJ: Coordination, Beam-target interactions, pellet generator
         GSI: Interfacing to PANDA
         UU: Real-time pellet tracking
         ITEP, MPEI: Pellet generator, simulations


                                               Technical drawings:
                                                  end of 2008

                                                Construction 2009+

Markus Büscher          PANDA collaboration meeting, Dubna, 04/07/2007   2
    How to produce frozen pellets




                                                                               Transition (“sluice”)
                   Triple point
                    chamber:
                 Liquid jet splits
                  into droplets                                                 Vacuum

                                                                             Flux of frozen pellets
                           Beam
                   (accelerator, laser, …)




Markus Büscher                       PANDA collaboration meeting, Dubna, 04/07/2007                    3
    Breakup of fluids …
  … has been at the focus of scientific research for a long time
                                          Rayleigh (1891)




                             Water jets




                    Savart (1833)


Markus Büscher           PANDA collaboration meeting, Dubna, 04/07/2007   4
    Drop formation …

    … is in general accompanied by satellite production (variation of drop sizes)


    Linear theories
 (e.g. Rayleigh, 1879)




                                                                            Water jets
        Non-linear
         effects




                         Rutland & Jameson, J. Fluid Mech. 46, 267 (1971)



Markus Büscher                       PANDA collaboration meeting, Dubna, 04/07/2007      5
    Jet breakup (linear theory)
   Dimensionless fluid parameters:
                 µ
    Oh                     Ohnesorge No.
                R0
             v jet  R0
    Re                     Reynolds No.
                 µ                                       2R0                     initial perturbation δ, o(100 nm)
                                                                                        with frequency fnozzle
                                                                                                                       Lord Rayleigh
                                                                                                                        1842 – 1919
 R z              γ / γ0   z 
                                                                                           Oh Re ln1/ δ 
                                                                 vjet              R0                                 Nobel Prize 1904
                    Oh  Re R 
         1  δ exp                                                  Ljet =
 R0                           0                                                 γ / γ0

                                                                                                 Verified for many fluids
                                                                                                    like water and oil

 /0 = growth rate

                                                                 
                                                                                           Observation (for water):
                                                                                   mono-disperse & satellite-free production
                                                                                              for X ≈ 0.69 only

                                                                                     (i.e. certain choice of jet parameters:
                                                                                                   vjet, fnozzle, R0)
                     X  2  R0 /  2  R0  fnozzle /v jet

Markus Büscher                                    PANDA collaboration meeting, Dubna, 04/07/2007                                   6
    Sources of unwanted vibrations


  Cooling devices (e.g. displacers in cold heads)

  Turbulent liquid flows

  Boiling (Tboil. – Tmelt. ≈ 5 K for H2, Ar, Xe, …)




Markus Büscher      PANDA collaboration meeting, Dubna, 04/07/2007   7
    Suppression of vibrations (1)
     • Cooling with cryogenic liquids
   T=300 K     H2     He THe=45.6 K                                  T=300 K Ar     N2


                                                             N2                                                 Ar
                                                                                                       T=77 K

                                  He
                                  He
                                                                                                  N2




                                                THe=4.5 K




                                   THe=16.2 K
      T=81 K

                       T=16.9 K


                                                THe=5.05 K



                            T=12 K                                                       T=87 K



                    H2 droplets                                                   Ar droplets

Markus Büscher                             PANDA collaboration meeting, Dubna, 04/07/2007                            8
    Suppression of vibrations (2)
     • Minimal temperature gradients
     • Constant level of liquefied target gas

                                 Heat                                   Precooled
                               exchanger                                H2 (N2, Ar…)

                                                                        He gas         He gas
                                                                        H2 (N2, Ar…)
                                             Heater                     for pressure
                                                                        regulation
                     Heater
           for temperature
                 fine-tuning                          Condenser
                                                                        Piezo



                                                         Glass nozzle



            ∆T < 5 K



Markus Büscher                  PANDA collaboration meeting, Dubna, 04/07/2007                  9
    Our pellet generators




              Jülich, FZJ                               Moscow, ITEP                                 Moscow, MPEI
 PANDA prototype target                       Thin liquid jets and pellets from N2, Ne,   Test of thermodynamic models for water
 Production of thin liquid jets and pellets   Ar, Kr and Xe. First observation of Ar      drop production. Development of optical jet
 from H2, D2, N2, Ar and other materials.     and Xe jets and pellets.                    and pellet diagnostics.

Markus Büscher                          PANDA collaboration meeting, Dubna, 04/07/2007                                             10
    PANDA prototype target
                                      Operation principles:
                                      • Vibration-free cooling
                                      • 3 cooling stages:
                                            • liquid N2 for pre-cooling
                                            • evaporated He gas in heat exchanger
                                            • evaporated He gas in condenser

                                      • Advantages:
                                           • No vibrations transferred to the nozzle
                                           • Jet generation from various gases:
                                                     H2, D2, O2, N2, Ne, Ar, Kr, Xe




                                      Apparatus and method protected by:
                                      Russian Federation Patent (№ 2298890)
                                      German Patent (Anmeldung 10 2007 017 212.7)




Markus Büscher   PANDA collaboration meeting, Dubna, 04/07/2007                        11
    Triple point chamber (TPC)

                            He cooling lines


                            condenser          Temperature and pressure in the TPC:

                                                         14 K, ~100 mbar for H2
                                                         83 K, ~800 mbar for Ar




                                                                  Vibrating nozzle




                                                                  Sluice to 1st vacuum chamber
                                                                    (ø ~ 0.5 mm, L~120 mm)




Markus Büscher   PANDA collaboration meeting, Dubna, 04/07/2007                                  12
    Droplet & pellet diagnostics

                                                 CCD cameras




Analysis software

Observation of
jets and individual
pellets

Measurement of
pellet size, shape,
velocity and
deflection angle
from the sluice
axis

Markus Büscher        PANDA collaboration meeting, Dubna, 04/07/2007   13
    Cryogenic droplets
 • First observation of mono-disperse and satellite-free
   droplet production for cryogenic liquids !!
     H2, ø = 12 µm   N2, ø = 17 µm           Ar, ø = 17 µm              Expectation for
                                                                          H2, N2, H20




        X = 0.60      X = 0.53
                                                    Deviations from (“good old”) linear theory?


Markus Büscher         PANDA collaboration meeting, Dubna, 04/07/2007                              14
    Deviations from linear theory !
  • Cryogenic jets are significantly more resistant to
    decay than predicted
                       H2, ø = 12 µm                   N2, ø = 17 µm
                                                                                                       Oh Re ln1/ δ 
                                                                                               R0
                                                                               LRay leigh =
                                  Lobserved                                                   γ / γ0
                 LRayleigh




                                                                   Lobserved
                                                      LRayleigh
                                                                                                        ?




                                                                                                            Submitted to PRL



  • Effect of surface evaporation …???
Markus Büscher                                PANDA collaboration meeting, Dubna, 04/07/2007                                    16
    New jet modes !
     • Decrease of TPC pressure and/or jet velocity
       stronger evaporation
       strong effect on jets (bending)

                  N2                  H2                                 water




                                  2R0 = 12 µm
                                 Vjet = 0.8 m/s.
                                  TTPC = 14 K
                                pTPC =130 mbar


               2R0 = 17 µm                                              2R0 = 150 µm
              Vjet = 1.0 m/s.                                     Vjet = 4.0 / 3.9 / 3.0 m/s.
               TTPC = 74 K                                              TTPC = 300 K
             pTPC =300 mbar                                      pTPC =3.0 / 0.8 / 0.9 mbar




                                                                                                Submitted to PRL

Markus Büscher                     PANDA collaboration meeting, Dubna, 04/07/2007                              17
    Properties of pellet flux
  • Stable pellet production observed for H2, N2, Ar
                                      Frozen H2 and N2 pellets behind the sluice to
                                      the vacuum chamber

                                      Observation of pellet tracks with CCD cameras




                                                                1 mm




                                                           –1      –0.5   0   +0.5   +1
                                               Radial pellet displacement (extrapolated to
                                                interaction point 1.2 meters below sluice)

Markus Büscher    PANDA collaboration meeting, Dubna, 04/07/2007                          18
    Ongoing tests (example)

  • Scattering of laser light off H2 pellets


                                           Target
                                           vacuum
                                          chamber




                                                                              Laser




                 Photomultiplier         … verification of narrow pellet beam

Markus Büscher               PANDA collaboration meeting, Dubna, 04/07/2007           20
    Future tasks

     • Complete automation system for target control

     • Test of the fast part of the diagnostic system

     • Stable production of pellets from O2, Ne, Kr, Xe

     • Develop and test a pellet generator for frequencies ~100kHz

     • Improve the droplet frequency stability after sluices

     • Update of thermodynamic model using new experimental results

     • Find sluice geometry for minimum angular distribution of pellets




Markus Büscher         PANDA collaboration meeting, Dubna, 04/07/2007     21
    Pellet generator @ PANDA




Markus Büscher   PANDA collaboration meeting, Dubna, 04/07/2007   22
    Our team
                          Forschungszentrum Jülich (FZJ)
                          M.Büscher, P.Fedorets, D.Spölgen

     Institute for Theoretical and Experimental Physics (ITEP), Moscow
            A.Gerasimov, V.Balanutsa, V.Chernetsky, A.Dolgolenko,
               A.Demekhin, V.Goryachev, L.Gusev, S.Podchasky

                 Moscow Power Engineering Institute (MPEI), Moscow
                       A.Boukharov, I.Maryshev, A.Semenov


                                          “Sponsors”:
           BMBF (WTZ 96/634, 99/684), COSY-FFE, DFG (436 RUS 113/561, 436 RUS 113/733),
                                EU/FP6, INTAS, ISTC 1966, RFBR



                                            Further info:
                            http://www.fz-juelich.de/ikp/pellet/index.shtml


Markus Büscher               PANDA collaboration meeting, Dubna, 04/07/2007               23

				
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