timing counter status
DESCRIPTION
Timing Counter Status. Timing Counter 2008 configuration Monitoring and Calibrations Timing resolution (TC and MEG). G.Cavoto INFN Roma Feb 18 th 2009. Timing Counter (TC). Two sectors, D own S tream and U p S tream, each with 15 scintillator bars readout by PMTs (TICP) - PowerPoint PPT PresentationTRANSCRIPT
G. Cavoto 1
Timing Counter Status
G.Cavoto
INFN Roma
Feb 18th 2009
Timing Counter 2008 configurationMonitoring and Calibrations
Timing resolution (TC and MEG)
G. Cavoto 2
Timing Counter (TC)
Two sectors, DownStream and UpStream, each with – 15 scintillator bars readout by PMTs (TICP)
» Trigger » Measure time, and z
– 256 Scint. Fibers readout by APDs (TICZ)» (Meant for) geometrical trigger selection » Measure z
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
G. Cavoto 3
Hardware upgradesNew EVAL bag for N2Very tight! He concentration at
few times atm. bkg level
Reduced APD noiseLight tight Tedlar foil added
Some maintenance work (fix connectors,cables…)Both US and DS TC remounted in late spring
G. Cavoto 4
TICZ readout tests After installation, test with ‘pass-thru’ cosmics
• All analog channels (8 APD in one ch.) show good signals!
• US TICZ digital readout working!• DS TICZ worsened
by higher environmental noise
• 3 (out of 8) DS TICZ readout sections failed during the 2008 run• “on-board” hardware problems: fixing deferred to 2009
US TICZ
fiber #
G. Cavoto 5
Laser system– Additional timing calibration device
» Providing 532 and 266 nm light at 50 Hz » Optical fibers distribution to TC bars (and XEC)
– Problems in operation:» environment temperature became too high
cavity unstable drift in the feedback signal
electronic saturation, damages of optical components and electronics.
3m cavity 48 MHz, 1064nmDiode pumped Nd:YVO
Acustic-optical pulse selectors
50 Hz2 stages pulse amplifier
50Hz @ 532nm
256 nm-For 2009 run:- Proper box with actively stabilized temperature- Retuning of cavity- New feedback electronics
G. Cavoto 6
PMT gain equalization
• Select Michel positron hitting bar center(magnetic field ON)
• Change HV to havesame average chargefor PMTs of the same bar
Bef
ore
Aft
er
G. Cavoto 7
TC measurements
DRS3 digit izat ion f or Double Threshold Discr iminator NIM pulses t0 and t1 extracted with waveform template fi t to NIM pulses.Checked with cross-correlati on method (opt imal f ilt ering).
t0 T h
veff b0
c0A0
e+
L
hPMT0 PMT1
t1 T L hveff
b1 c1A1.
T : time of positron at the impact point on first hit bar (connected to the positron track from DCH)
h : impact point along bar length (z direction)
effective velocity
amplitude of PMT signal
G. Cavoto 8
TC calibrations Timing with DTD NIM signals
c0
c1
L
2veffb0 b12
b0 b1
Time walk correction for each PMT
Michel nmult=3
Time offset between PMT of the same bar (z offset calibration)
Cosmics
Relative time offset between bars
Boron
Effective velocity for each bar
(z measurement)
Pass-thru cosmics
Absolute time offset between positron
and gamma
_ Dalitz 0
0 e(e )
veff
B(p,)C
G. Cavoto 9
‘Double’ and ‘triple’ hit events
TA
TB
On sample of two hit adjacentbars (‘doubles’) test time walk correction (c0 and c1)
|z|
bar
#
e+
TC
t0C t0B2
t0A 1
2
c0CA0C
c0BA0B
c0AA0A
.
1st bar
On events with three adjacent hit bars (triples)minimize the differences (for all the bars)
T TA TB
ns
G. Cavoto 10
TC time resolution
Upper limit on average time resolution () in 60-90ps range
Includes effect of DRS digitization (~10 ps)
(estimated sending same signal to two DTD inputs)
Estimate of single bar time resolutionAssuming the two bars to have the same intrinsic time resolution
T
2
G. Cavoto 11
TC time resolution stability
• Same TW calibration constants
• Stable over timeno need of different sets of constants
Runs 24xxxRuns 25xxxRuns 26xxxRuns 27xxxRuns 29xxxRuns 30xxxRuns 31xxx
G. Cavoto 12
Inter-PMT offsets
Dedicated cosmics runs taken in different down-time periods– Select event with 1 or 2 hit bar
Assume symmetric distribution along the bars
Most of the bars have this flat distribution
t1 - t0 [ns]
Data taken in different periods very consistent (TICP very stable!!!)
G. Cavoto 13
MEG physics runs TC hitmap
t1-t0 [ns] t1-t0 [ns]
Distribution nicely “justifies”
Need veff to have the correct z scale
Before After
DS
US
G. Cavoto 14
Effective velocity with TICZPass-thru cosmics, 2 hit fibers (clusters) expected
Single-cluster inefficiency: 27%
due to cosmics geometrical inefficiency + dead/hot fibers (5%)
zbar-zfiber (cm)
Bar16
z fiber 1
2veff (t1 t0)Using
v eff (c
m/n
s)
Syst err.1.5%
G. Cavoto 15
Inter-bar offset extraction
• Gaussian fits.– Cosmic background evaluated in runs with no-beam and
same trigger requirements (TC & XEC)
• Syst error on calibration constants at 50ps level
T[ns]
Bar17-signal-bkg (rescaled)
Bar14-signal-bkg (rescaled)
T[ns]
Boron events 4.4MeV (XEC) and 11.7MeV(TC)
T TXEC LXEC
c
t0 t12
LTC
c
G. Cavoto 16
Inter-bar offsets monitoring
Sep08/1013/1020/1025/1010/1124/1101/12
Tmean [ns]
bar#
- No clear trend vs time- Relative offsets stable
Bar15: change in DRS board
tim
e
relative to bar 17
Weeklymonitoring(periodic DB updates)
G. Cavoto 17
DCH-TC match hitmap
Extrapolate tracks from DCH to TC bars
Given a track and a TC bar hit matching efficiency is 91%Some data/MC discrepancy
zzDCH zbar [cm]
G. Cavoto 18
MEG absolute time offset Dalitz 0 events
– Same topology as signal !
– Gamma/positron energy range (can be chosen) same as for signal
– Worse resolution due to LH2 target Comparison with signal is not exact
0 e(e )
ns
Te TXEC LXEC
c
T
LeTC
c
Centre of signal window
Control sample (flight length correction)
MC validation
Bar17μ = 26.06±0.01ns = 267±10ps
G. Cavoto 19
Timing systematics check
Boron (E=4.4MeV)
bar#
T
(e
) [n
s]
Dalitz (E>45MeV)
Residual time walk effecton XEC timing
Dalitz before calibration
Dalitz after calibrationwith Boron
bar#Residual inter-bar differences(different target for 0 Dalitz)
T
(e
)-T
(
e)(b
ar1
7) [n
s]
Relative to bar 17
G. Cavoto 20
Summary
• TICP very stable over the 2008 run.• TICZ: 13 out of 16 sectors working. • Calibration strategy developed and
successfully applied to data.• Data monitored during data-taking.• Some fine-tuning still needed
– Residual bar differences – Detailed data-MC comparison
G. Cavoto 21
Outlook for 2009
– Detector activity• New APD electronics
– Shorter shaping time to fit trigger timing– Currently prototyping new el. boards
• LASER• Upgrade of TC slow control
– On track for a 2009 data-taking period
– Data analysis• Calibrated TC data and TC simulation available for MEG
analysis• MEG timing measurements well underway
G. Cavoto 22
Back up
G. Cavoto 23
New APD electronics
• Requirements: – fast signal ( 3-5 times faster) 15ns achievable.– better EMI immunity– Implement redundant schemes for the command transmission (I2C)– Improve over all settings capability ( on board test /calibration signal,…)- Bread-boarding is started, final design of the prototype board will be
sent for the production by Dec 08.
Test pulse response
Move Amplifier tothe APD board and/or differential input
To insert APD into trigger