Trigger
NUpeth U(t)=
Npe 5 Npe
50 Npe
CFD in fADC channel
pe U(t) N dc (t)
U pe U(t)
3 N ) 2 pe U(t
N 3)
(1+2 ⋅ ⋅ − + ⋅ ⋅ = + + ⋅
− noise
U(t) Npe
1 Npe
(t) Npedc
U(t) U 3 ) 2 U(t 3)
(1+2 ⋅ − + ⋅ = + + ⋅
− noise
by Jim Buckley, WBS SP7
Optimization
delay 1.55.5ns
CFD rate feedback
f2V
Variable gain
Time walk optimization PMT
signal
Discriminator threshold adjustment
Zero crossing comparator
Programmable width
Coincidence resolving time adjustment
fraction
Threshold discriminator
D CLK
Q R
Schematic
RFB
RFB benefit
• Rate compression
• Dispersion (jitter)
• Time walk (jitter)
• Efficiency
Rate vs Threshold
RFB=0
Pulse Start Time Dispersion
NSB=0.2 pe/ns Pulse = 7 pe Threshold =5 pe RFB=60
Pulse Start Time Dispersion vs NSB
Pulse = 7 pe Threshold =5 pe
RFB=60 (minimizes dispersion)
Time walk vs RFB
Pulse = 7 pe Threshold =5 pe NSP=0.8 pe/ns
(dc offset is dynamical)
Trigger Efficiency vs RFB
NSB=0.8 pe/ns Pulse = 7 pe
CFD output pulse width
NSB and ? noise
fADC ped sigma (WU_CFD)
0 0.5 1 1.5 2 2.5 3 3.5
0 0.2 0.4 0.6 0.8 1
NSB (pe /ns)
ped sigma (fadc dc)
Noise in WU CFD
dc offset = 2440 dc (???)
Rate vs Offset (W U9)
1 .00E+00 1 .00E+01 1 .00E+02 1 .00E+03 1 .00E+04 1 .00E+05 1 .00E+06 1 .00E+07 1 .00E+08 1 .00E+09
1700 1800 1900 2000 2100 2200 Offset (d c count)
Rate (Hz)
Noise in UU CFD
Rate vs RateFeedback (UU40)
1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09
0 50 100
Rate Feedback setting (dc count)
Rate (Hz)
Rate vs. threshold WU9
Rate vs Threshold
1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09
2200 2300 2400 2500 2600
Threshold (dc count)
Rate (Hz)
NSB=0.1 NSB=0.2 NSB=0.4 NSB=0.8
Rate vs. threshold UU40
Rate vs Threshold (UU40)
1.00E +00 1.00E +01 1.00E +02 1.00E +03 1.00E +04 1.00E +05 1.00E +06 1.00E +07 1.00E +08
5 0 5 10
Threshold (pe)
Rate (Hz)
NSB =0.1 pe/ns
NSB =0.2 pe/ns
NSB =0.4 pe/ns
NSB =0.8 pe/ns
Jitter (on fADC board)
CFD Jitter NSB=0
0.05000 0.00000 0.05000 0.10000 0.15000 0.20000 0.25000 0.30000 0.35000 0.40000
36.5 3737.5 3838.5 3939.5 4040.5 4141.5 4242.5 4343.5 4444.5 4545.5 4646.5 4747.5 4848.5 4949.5 5050.5 5151.5 5252.5 5353.5 5454.5 5555.5 5656.5 5757.5 5858.5 5959.5 6060.5
W U9 UU40 UU1 UU2 UU3 UU4
Sigma WU=0.73 ns; Sigma UU=1.331.73 ns
Pulse = 7 pe Threshold =5 pe RFB=60
“ WUlike”
CFD Jitter (UU1 at different pedestal values)
0.05000 0.00000 0.05000 0.10000 0.15000 0.20000 0.25000 0.30000 0.35000 0.40000
44 44.5 45 45.5 46 46.5 47 47.5 48 48.5 49 49.5 50 50.5 51 51.5 52 52.5 53 53.5 54 54.5 55 55.5 56 56.5 57 57.5 58 58.5 59 59.5 60 60.5
W U9 UU1RFB60 UU1RFB80 UU1RFB100
CFD pulse Width
C FD Pulse W idth D istribution
0.10000 0.00000 0.10000 0.20000 0.30000 0.40000 0.50000 0.60000 0.70000 0.80000
00.5 11.5 22.5 33.5 44.5 55.5 66.5 77.5 88.5 99.5 1010.5 1111.5 1212.5 1313.5 1414.5 1515.5 1616.5 1717.5 1818.5 1919.5 2020.5 2121.5 2222.5 2323.5 2424.5 2525.5 2626.5 2727.5 2828.5 2929.5 30
CFD P ulse W idth
W U9 NS B = 0.1 pe/ns UU40 NS B =0.1 pe/ns W U9 NS B = 0.8 pe/ns UU40 NS B =0.8 pe/ns
Mean time change
CFD Pulse W idth M ean
18.00 18.50 19.00 19.50 20.00 20.50 21.00 21.50 22.00
0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80
NSB [pe/ns]
Pulse Width Mean [ns]
W U 9 U U 40
CFD pulse width dispersion
CFD Pulse W idth Dispersion
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50
0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80
NSB [pe/ns]
Pulse Width Dispersion [ns]
W U9 UU40
UU_CFD vs. WU_CFD
• CFD output pulse width is programmable
• CFD output pulse width stability
• Fraction vs. delay lines optimized (no 2nd DL)
• DC offset > RFB (demonstrated in the lab)
• Noise problem (500 MHz ?)
• Jitter has increased (on fADC board)
• RFB malfunctions since NSB < ? noise
Plans ?
• Layout review when ?, cost?
• Layout change (fADC, CFD, CFD test board) when will we know about this ?
who makes the decision?
• Gain increase ?
will this work (test on fADC)
• fcasfc
Options
