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Peter Križan |
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University of Ljubljana and J. Stefan Institute |
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For Belle Aerogel RICH R&D group |
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K/p separation at 4 GeV/c |
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qc(p) ~ 308 mrad ( n = 1.05 ) |
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qc(p)– qc(K) ~ 23 mrad |
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dqc(meas.) = s0 ~ 13 mrad |
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With 20mm thick aerogel and 6mm PMT pad size |
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ŕ
6s separation with Npe~10 |
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Reported last year: better optical quality for n~1.05 hydrophobic aerogel |
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a new solvent (Di-Methyl-Formamide instead of
Methyl-alcohol) |
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precursor (Methyl-silicate-51) from a different
supplier |
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-> considerable improvement |
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Cut into hexagonal shape from a square block |
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Machining device: use “water-jet” thanks to
hydrophobic nature |
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Baseline: large area HPD of the proximity
focusing type |
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Backup: MCP-PMT |
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Study uniformity of the sensitivity over the
surface |
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Gain：5 [V/pC] |
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Shaping time：0.15 [μs] |
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S/N
：8 (@2000[e]) |
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Readout ：pipeline with shift register |
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Package : 18 channels/chip |
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Proof of principle shown already last time. |
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More photons: employ radiators with multiple
refractive indices. Idea successfully tested in beam tests. |
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Aerogel production: transmission length
improved, new cutting methods tested, multiple layer samples. |
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R&D issues: development and testing of a
multichannel photon detector for high mag. fields |
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mass production of large aerogel tiles |
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readout electronics |
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Total number of readout channels for the full
detector amounts to 86k. |
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Detector
characteristics |
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Leakage
current: 10 or 25［nA］ |
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Detector
capacitance: 10 or 70 ［pＦ/pixel］ |
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signal: 2000
or 20000 [electron/photon] |
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Need
high density front-end electronics. |
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Need
high gain with very low noise amplifiers. |
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Deadtimeless readout scheme-> Pipeline. |
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Develop an ASIC for the front-end electronics |
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Basic parameters for the ASIC (Rohm CMOS 0.35μm) |
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Gain：5 [V/pC] |
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Shaping time：0.15 [μs] |
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VGA：1-16 |
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S/N
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Readout ：pipeline with shift register |
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Package : 18 channels/chip |
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Control : LVDS |
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Power consumption : 5 m W/channel |
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Detailed evaluation is under way. |
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Diode : □5 [mm/ch] |
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Gain :
26000 [electron/photon] |
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Cd : 73 [pF] |
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IL
: 14 [nA] (average/ch) |
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Condition: VHV=8[KV], VBIAS=320[V] |
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In agreement with expectations (+ 6-8 mrad) |
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Typically around 13 mrad (for 2cm thick aerogel) |
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Shown as a function of thickness, momentum |
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Shown as a function of momentum, thickness |
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From typical values (single photon resolution
13mrad and 6 detected photons) we can estimate the Cherenkov resolution per
track: 5.3mrad; |
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-> 4.3sigma p/K separation a 4GeV/c. |
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sq is obtained by fitting the q distribution
Gaussian + background |
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Scan with the beam across the tile boundary. As
expected, the yield is affected over a few mm in the vicinity of the
boundary. |
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A simple model (all photons hitting the boundary
get lost) accounts for most of the dependence |
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92% of the surface covered by HPDs |
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minimal distance between modules: 0.5~mm |
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max. distance (few mm) allows for feeding in the
HV supply cable (has to come to the front side of the HPD) |
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six equal sectors |
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Notes