Örjan nordhage gsi/uppsala university germany/sweden a high-density pellet target for antiproton...
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ÖRJAN NORDHAGEGSI/Uppsala University
Germany/Sweden
A high-density pellet target for antiproton physics with
2nd Swedish Workshop on FAIR Physics, Lund, September 12-13, 2005
Sept. 12, 2005 Örjan Nordhage, 2nd SFAIR meeting 2
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, 2005 Örjan Nordhage, 2nd SFAIR meeting 3
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, 2005 Örjan Nordhage, 2nd SFAIR meeting 4
Target thickness at or HESR
Number of antiprotons: 1×1011
Momentum range: 1.5 – 15 GeV/c (β: 0.848 – 0.998)
HESR circumference: 574 m
Design luminosity: 2×1032 cm-2s-1
AN
A
NfL trev 2t atoms/cm 15105.4
A
NA
The reaction pp means a pure hydrogen targetand
currently, pellets (frozen micro-spheres) are the only proven working solution, which provides such an effective target thickness
Sept. 12, 2005 Örjan Nordhage, 2nd SFAIR meeting 5
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, 2005 Örjan Nordhage, 2nd SFAIR meeting 6
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
[Ö.N. et al., NIM A 546 (2005)]
What gets through is very close to homogenously distributed
Sept. 12, 2005 Örjan Nordhage, 2nd SFAIR meeting 7
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
mm
mm expip
geomip
1.2
0.2
S
SPellet beam scan (Deuterium), 0.59 mm
1.00E-07
1.00E-06
1.00E-05
-2 0 2
Tilt angle (mradians)
Pre
ssu
re x'-angle
y'-angle N.B. Target geometry (skimmer position and diameter Φ) alone define Sip
Sept. 12, 2005 Örjan Nordhage, 2nd SFAIR meeting 8
Target thickness and pelletsPellets are discrete and locally very thick ~ 1020 atoms/cm2
Thus, the effective thickness needs an associated area
distancepellet interaverage the is
point on interactitheat spreadpellet the is
where
ip
ippellett
-l
S
lSA
Pel
let
beam
‹l›
Antiproton beamSip
Maximum luminosity if beam area and target area are matched
lS ~height and ~ width (full) beam antiproton :Thus ip,
N.B. Not in
scale:
beam (~mm) >
> pellet (~
30μm)
Sept. 12, 2005 Örjan Nordhage, 2nd SFAIR meeting 9
Pellet requirements at or HESR
With215105.4 atoms/cm req
eff
we need pellets of a certain size, and how often?
Last H2 run (Dec. 2003): f~9000/s, 33μm, 95m/s
A factor less than 2 off from is already achieved
reqeff
R&D
Sept. 12, 2005 Örjan Nordhage, 2nd SFAIR meeting 10
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 spreadSpread 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, 2005 Örjan Nordhage, 2nd SFAIR meeting 11
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, 2005 Örjan Nordhage, 2nd SFAIR meeting 12
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, 2005 Örjan Nordhage, 2nd SFAIR meeting 13
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, 2005 Örjan Nordhage, 2nd SFAIR meeting 14
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, 2005 Örjan Nordhage, 2nd SFAIR meeting 15
R&D: Pellet Tracking/Profile System
Basic idea:
ΔyΔyΔy
x1x2
z
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, 2005 Örjan Nordhage, 2nd SFAIR meeting 16
Pellet Target in the -detector
3.7m
(Corresponding distance for WASA: 3.3m)
Sept. 12, 2005 Örjan Nordhage, 2nd SFAIR meeting 17
215105.4 atoms/cm reqeff
N.B. 12.5m in z-direction
Pellet Target in the -detectorHESR-vacuum distribution for two different pellet sizes, but the same target thickness
%8.4
%2.3
1
105.4
2.35.1
20
9.105.1
30
215
2
2
mm
μm pellet
gas
mm
μm pellet
gas
pelletsbeam
reqeff
have we , and
atoms/cm For
S
B
S
B
N
Define: ’background due to gas to signal from pellet’-ratio
pelletsbeampellet
beam
pelleteffpellet
gas
pellet
gas
NA
A
L
dzz
S
B 1)(
Sept. 12, 2005 Örjan Nordhage, 2nd SFAIR meeting 18
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, 2005 Örjan Nordhage, 2nd SFAIR meeting 19
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, 2005 Örjan Nordhage, 2nd SFAIR meeting 20
Pellet requirements at or HESR
The pellet size goal is determined by the inter-pellet distance that could be matched by the antiproton beam
215105.4 atoms/cm reqeff
N.B. The plot is independent of pellet speed