Status of TPC experiment ---- Online & Offline M. Niiyama H. Fujimura D.S. Ahn W.C. Chang.
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Transcript of Status of TPC experiment ---- Online & Offline M. Niiyama H. Fujimura D.S. Ahn W.C. Chang.
• From cosmic ray test, 1 track resolution is - 300 um in pad plane w/ magnet- 700 um in drift direction w/o magnet.
• If we apply magnetic field, residual in drift direction shifts layer by layer. Possible reason are
- circle fitting is not suitable for our solenoid magnet. -> runge kutta is needed - E x B effect disturbs drift property of electrons in TP
C. Bx at z=350mm is 0.5T -> simulation of drift property is needed.
Results from cosmic ray test
Install & Geometry
151.6 cm 40.7cm
20cm
32.4cm
Collimator Shield target
TPC
solenoid
Pb
Top view
Dip
ole m
agn
et
37.5 cm
dipole magnet
Downstream scintillators
Side scintillators
Shield
Collimator
Upveto
EXP.HUTCH( February )
February run
dipole magnet
Downstream scintillators
Side scintillators
Shield
Collimator
Upveto
EXP.HUTCH(March)
Start counter
TOF Wall
Veto @TOF
March run
Trigger condition
• Run in Feb, to know performance of TPC
tag x (up-veto) x (8scinti M>=2) x (TPC side scinti M>=1)
95Hz at 400kHz tagger• Run in Mar, Particle ID by spectrometer calibration of TPC.
gamma-> pi+ pi- p, trigger is similar as K0 exp.
- tag x (ATG) x (TOF M>=2) x (veto after TOF)
x (TPC side scinti M>=1)
• At least one particle comes from target holder• Reject if two tracks overlap each other
Scanning criteria
Analysis
• dE is measured by pad rows• By correction by dip angle between pad plane and track was
applied.• Truncated mean was used to suppress Landau distribution.
- for each track, to get truncated mean,
- cut the Landau tail of the distribution
- keep 60% of the sample, which have the most lowest amplitude
- get the mean value of the remaining distribution
truncated mean• Circle fitting in pad plane, line fitting in arclength z plane• dE/dx value of given tracks• Cut condition ; chi2 for pad plane and arclength z plane
Momentum/charge
(dE
/dx
Tru
nca
ted
me
an)
*co
s(la
mb
da)
• Calibration of gain is not finished.• Runge-Kutta tracking is not yet used. Just circle fitting for p_t determination
proton
Pions or electrons
1000 events eyescan
DAQ Speed
Goal: 100 Hz. In total 3 SUN SPARC (collector) to read out data in
parallel. Feb run:15Hz.
# of words read =10000-30000 word, for 1 IRQ( = 4events), 1 module
Unstable pedestal: drifting with temperatures. (Air-condition is desirable.)
March Run: 20Hz On-board width-cut for discrete pulses (<4 time bins). Tag*\bar{up}*ATG*\bar{e+e-}*(TOF M>=1) * (TPC side M>=2) # of words = 3000, 1 IRQ( = 4events) for 1 module
Where is the bottle neck of DAQ speed? Reduce the number of sampling to 600. Reduce the CLOCK from 40 MHz to 20 MHz. Look for the other possible source in collector or builder.
TPC analyzer 1
Pad 1
pulse1 Pulse2 ……….
ADCTDC
ADCTDC
Pad 2
pulse1 Pulse2 ……….
ADCTDC
ADCTDC
If overlap in time direction was foundin adjacent pad they are include in a cluster.
Pad 3
pulse1 Pulse2 ……….
ADCTDC
ADCTDC
Continue in all pads in layer while overlap is found
In one layer
Pad#
Time
TPC analyzer 2
In one layer
Cluster Hit
x, y, z coordinateADC
To reduce # of hits to be searched by find track. Select hits of enough large ADC.
BoneHit
x, y, z coordinateADC
TrackFinder
Under construction
TrackFinder
Track pattern recognition: Segment the acceptance into sub-volumes in
(r,,z). Nose-finding algorithm: pick up hits on the
most outer layer and search the nearest hit in the neighboring sub-volume inwards.
Construct track-candidates: after conformal mapping, make the cut on the chi2 values of a straight line fit.
Track Parameters for RK fitting: Assuming uniform B field. Circle fitting on the transverse plane: (x0,y0)
and (Px0,Py0) Slope of arclength vs z: (z0) and Pz0.
Runge-Kutta Fit with real B field map.
TPC Analyzer
Input file: MC ntuples or real data. Output ntuples: hits information and
track parameters. Test with MC ntuples. Test with real data.
Conclusion
TPC has started operation in this Feb. We are taking data now with triggers from
both tracks in TPC and spectrometer. Struggling with large data size and slow
DAQ speed. Need to improve it significantly.
Need to demonstrate the ability of track-finding and PID.
We need helps from other LEPS members for data-taking and offline analysis.