Analysis of TOF data
Yordan Karadzhov
St.Kliment Ohridski University of Sofia
1
Layout of the TOF system in Frascati test
PMT left
scintillator
PMT right
TOF bar
electron beam
finger 1
Bar 1
Bar 2
DAQ system
Bar 3
finger 2
2
List of analyzed runs
•
•
•
•
•
Run
Energy
TDC
124-133
141-149
215-217
250-255
255-259
350 MeV
300 MeV
200 MeV
350 MeV
350 MeV
V1290
V1290
V1290 & V775
V1290 & V775
V775
Splitter Discriminator
Active
Active
Passive
Passive
Passive
CAEN N417
CAEN N417 & PLS 711
CAEN N417 & PLS 711
PLS 711
CAEN N417
Because of the poor statistics we need to use a chain
of runs taken in same conditions (experimental setup)
and same beam energies.
3
ADC pulse height distribution
(left PMT of bar 1)
Example of the general event selection cut
ADC spectrum in
logarithmic scale
Selection of single
electron events
Part of the same
spectrum in linear
scale
4
Intrinsic time resolution of the TOF bar
T

T T

T
TOF


2
2
bar
2 bar
2
bar
1 bar
1
left
right
left
rig
bar
2

bar
1
Timebar2
Timebar1
T

T


left
right





T
_
bar
 2 
n


The quantity (Tleft – Tright )/2 has the same variation as
(Tleft + Tright )/2 but time jitter cancelled out, so the intrinsic time
resolution of the bar could be evaluated more conveniently from
its distribution.
5
Intrinsic time resolution of TOF bars
Run 141 – 149
Distributions of (Tleft – Tright )/2
TDC V1290
Bicron BC420 - 4cm thick
impact point at 10cm from
Center
Discr CAEN N417
σ = 63.91 ps
Bicron BC420 - 4cm thick
impact point at center
Discr PLS 711
σ = 66.18 ps
Bicron BC408 - 6cm thick
impact point at center
Discr PLS 711
σ = 109.7 ps
6
Intrinsic time resolution of TOF bars
Run 124 – 133
Distributions of (Tleft – Tright )/2
TDC V1290 Discr CAEN N417
Bicron BC420 - 4cm thick
impact point at 15 cm from center
(5 cm from edge)
σ = 72.73 ps
Bicron BC420 - 4cm thick
impact point at center
σ = 64.91 ps
Bicron BC408 - 6cm thick
impact point at center
σ = 107.2 ps
7
Intrinsic time resolution of TOF bars
Run 215 – 217
Distributions of (Tleft – Tright )/2
TDC V1290
Bicron BC420 - 4cm thick
impact at center
Discr CAEN N417
σ = 44.22 ps
Bicron BC420 - 4cm thick
impact point at center
Discr PLS 711
σ = 97.16 ps
Bicron BC404 - 6cm thick
impact point at center
Discr PLS 711
σ = 49.21 ps
8
Intrinsic time resolution of TOF bars
Run 215 – 217
Distributions of (Tleft – Tright )/2
TDC V775
Bicron BC420 - 4cm thick
impact point at center
Discr PLS 711
σ = 94.16 ps
Bicron BC404 - 6cm thick
impact point at center
Discr PLS 711
σ = 41.61 ps
9
Intrinsic time resolution of TOF bars
Run 250 and 251
Distributions of (Tleft – Tright )/2
TDC V1290
Bicron BC420 - 4cm thick
impact at center
Discr PLS 711
σ = 47.24 ps
Bicron BC420 - 4cm thick
impact point at center
Discr PLS 711
σ = 115.4 ps
Bicron BC404 - 6cm thick
impact point at center
Discr PLS 711
σ = 71.63 ps
10
Intrinsic time resolution of TOF bars
Run 250 and 251
Distributions of (Tleft – Tright )/2
TDC V775
Bicron BC420 - 4cm thick
impact at center
Discr PLS 711
σ = 49.95 ps
Bicron BC420 - 4cm thick
impact point at center
Discr PLS 711
σ = 101.4 ps
Bicron BC404 - 6cm thick
impact point at center
Discr PLS 711
σ = 66.67 ps
11
Intrinsic time resolution of TOF bars
Run 255 – 259
Distributions of (Tleft – Tright )/2
TDC V775 Discr
Bicron BC420 - 4cm thick
impact at center
CAEN N417
σ = 90.76 ps
Bicron BC420 - 4cm thick
impact point at center
CAEN N417
σ = 83.47 ps
Bicron BC404 - 6cm thick
impact point at center
CAEN N417
σ = 105.4 ps
12
Run
124-133
141-149
215-217
215-217
250-251
250-251
255-259
Energy
350 MeV
300 MeV
200 MeV
200 MeV
350 MeV
350 MeV
350 MeV
TDC
Splitter
Discriminator
V1290
Active
CAEN N417
BC 420 – 72.73 ps
V1290
Active
CAEN N417
BC 420 – 64.91 ps
V1290
Active
CAEN N417
BC 408 – 107.2 ps
V1290
Active
CAEN N417
BC 420 – 63.91 ps
V1290
Active
PLS 711
BC 420 – 66.18 ps
V1290
Active
PLS 711
BC 408 – 109.7 ps
V1290
Passive
CAEN N417
BC 420 – 44.22 ps
V1290
Passive
PLS 711
BC 420 – 97.16 ps
V1290
Passive
PLS 711
BC 404 – 49.21 ps
V775
Passive
CAEN N417
BC 420 –
V775
Passive
PLS 711
BC 420 – 94.16 ps
V775
Passive
PLS 711
BC 404 – 41.61 ps
V1290
Passive
PLS 711
BC 420 – 47.24 ps
V1290
Passive
PLS 711
BC 420 – 115.4 ps
V1290
Passive
PLS 711
BC 404 – 71.63 ps
V775
Passive
PLS 711
BC 420 – 49.95 ps
V775
Passive
PLS 711
BC 420 – 101.4 ps
V775
Passive
PLS 711
BC 404 – 66.67 ps
V775
Passive
CAEN N417
BC 420 – 90.76 ps
V775
Passive
CAEN N417
BC 420 – 83.47 ps
V775
Passive
CAEN N417
BC 404 – 105.4 ps
13
Time of Flight and Time-walk effect
• Because leading edge discriminator has been
used for the time measurements, the time-walk
effect should occur.
• Time-walk should effect measured TOF
especially in cases when we have different total
charge collected in the bars.
• This effect can be suppressed by constrain on
difference in ADC pulse heights (signals with
same pulse heights will give approximately same
time-walk).
14
Time of Flight and Time-walk effect
Run 124-133
no constrain
σ = 134.7 ps
bar
1
bar
2
ADC

ADC
rightPMT
rightPM

0
.
25
bar
1
ADC
rightPMT
σ = 123.5 ps
bar
1
bar
2
ADC

ADC
rightPMT
rightPM

0
.
10
bar
1
ADC
rightPMT
σ = 91.27 ps
15
Time Of Flight and Time-walk effect
Run 124-133
ADCbar1right  ADCbar1left ADCbar 2 right  ADCbar 2 left
ADC 

2
2
16
Conclusions
• Intrinsic resolution of the bars made of BC404 or BC420
is satisfactory. BC 408 is significantly worse.
• Passive splitter gives better performance than active.
• TDC V775 gives a little bit better results than V1290.
• We need more detailed investigation of the relation
between intrinsic time resolution and position of the
impact point.
• The effect of time-walk is significant and should be
corrected for.
17