c.woody, phenix upgrades, 11/10/00 a tpc for phenix ?? no, surely you must mean for star…. phenix,...
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C.Woody, PHENIX Upgrades, 11/10/00
A TPC for PHENIX ??
No, surely you must mean for STAR….
PHENIX, really …. ???
You must be NUTS !!!
Well, wait a minute...
Maybe we should think about this ….
C.Woody, PHENIX Upgrades, 11/10/00
Many Thanks to a Number of STAR Colleagues for Enlightening and Useful Discussions (and several nice pictures)
* H.Wieman* N. Smirnoff J. Thomas T. Hallman M. Messer
And several PHENIX Colleagues as well...
Y. AkibaA. DreesI. TserruyaE. Kistenev
C.Woody, PHENIX Upgrades, 11/10/00
Why a TPC for an inner tracker/electron identifier for PHENIX ?
• Excellent position resolution (STAR: srf~ 500 mm, sz ~ 1mm)• Excellent two particle resolution (STAR: ~ few mm)• Provides additional tracking information near the vertex• Would improve momentum resolution by tracking in field• Can naturally provide 2p tracking coverage• Provides electron identification by dE/dx
• Long drift time can limit rate capabilities• Possible space charge limitations at high track densities• Diffusion ultimately limits spatial resolution• Must have sufficient sampling to do good dE/dx measurement• Requires large number of readout channels (=> high cost)
C.Woody, PHENIX Upgrades, 11/10/00
PHENIX Central Region
5347
80
1600
60 40 37.5
C.Woody, PHENIX Upgrades, 11/10/00
dE/dx works well for e/p separation < 1 GeV
Requires good sampling !
Dalitz rejection Find soft electron by dE/dx
e+
e-
TPC
C.Woody, PHENIX Upgrades, 11/10/00
Interaction Rates (PHENIX CDR)
10x Design Luminosity
Drift times of 5-10 ms should be ok for most heavy ion running
Will certainly have pileup for pp and light ion running
How much of a problem is event pileup ?
Can PHENIX electronics handle 5-10 ms drift times ?
Beams Type L (cm -2s -1 ) Rate (kHz) T avg ( ms)
p + p MB 1.1 x 10 31 454.0 2.2
O + O MB 1.6 x 10 29 179.3 5.6
Si + Si MB 7.1 x 10 28 118.5 8.4
Cu + Cu MB 1.7 x 10 28 47.3 21.2
I + I MB 5.1 x 10 27 23.3 43.0
Au + Au MB 2.2 x 10 27 13.9 72.2
C.Woody, PHENIX Upgrades, 11/10/00
Fast drift gases - CH4 and CF4
10 cm /ms
12 cm /ms
40 cm drift => ~ 3-4 ms Requires high drift field
CF4 -Ar
CH4
C2 H4
(1 KV/cm) (1 V/cm/Torr)
C.Woody, PHENIX Upgrades, 11/10/00
Slower drift gases - He-C2H6
200 mm / cm
Diffusion
Drift velocity ~ 5 cm/ms
40 cm drift => 8-10 ms
Transverse diffusion ~ 1.3 mm
C.Woody, PHENIX Upgrades, 11/10/00
Diffusion in STAR P10 Gas
C.Woody, PHENIX Upgrades, 11/10/00
Is is Possible to Achieve Good Spatial Resolution and dE/dx Sampling Over a Limited R Range ?
• MSGC• GEM• MICROMEGAS• ...
Micropattern Detectors (~ 40-50 mm spatial resolution)
Kapton Hole Pattern GEM Cross-Section
Avalanche
C.Woody, PHENIX Upgrades, 11/10/00
STAR Inner TPC (R&D by H. Wieman & N. Smirnoff)
1 m
2 m
Inner TPC(20 cm < R < 60 cm)
Radiator
UV Sensitive Pad Plane Tracking + Electron ID
C.Woody, PHENIX Upgrades, 11/10/00
~ 1.8 m
4 Longitudinal Segmentations(limiting drift time,space charge)
STAR Inner TPC (R&D by H. Wieman & N. Smirnoff)
C.Woody, PHENIX Upgrades, 11/10/00
TPC w/4Longitudinal Segmentations (~ 40 cm drift each)
Inner Vertex Detector (Si Pixels)
STAR Inner TPC (R&D by H. Wieman & N. Smirnoff)
UV Sensitive Pad Plane
C.Woody, PHENIX Upgrades, 11/10/00
Should We Really Consider an Inner TPC for PHENIX ?
• Could provide necessary e/p separation for Dalitz rejection• Could provide 2p tracking for jet physics• Would significantly improve momentum resolution• Would provide additional tracking information near the vertex• Could be combined with a Si pixel vertex detector
• Needs significant study, simulation and R&D• TPC’s are best built by experts (do we have any in PHENIX ?)• Requires significant development in electronics and readout• Cost - Not Cheap !• Time scale - Not Short (> 3-5 yrs)