Update on LAV electronic
M. Raggi, P. Valente
G. Corradi, D. Tagnani, C. Paglia
LNF electronic service
LAV working group
LNF 4/12/2009
1
Outline
 Signal flanges DB37 solution update
 HV system (distributors, connectors)
 Improving PMT divider performance
2
DB 37 flanges ECOVIDE projects
10 DB37 connectors
Already asked for greater inter
connector distance (30mm)
15 DB37 connectors
Verified that 24 mm is enough with
proper air side connector. Cabling
difficulties to be evaluated in the
vacuum side
3
DB37 connectors solution
20 mm
Air
Vacuum
Vacuum
Air
Bring cables from the PMT to the back of the green connector on the right
Minimize the discontinuity between the PMT and the electronic
Reduce the number of connections in the cabling (less connectors)
4
HV system
5
HV connectors
HV connector
 The distance between lateral pins and
external connector crown is too small
– Up 1.5 KV high voltage present
– Inter pin distance max gap is only 0.5 KV
– Asked ECOVIDE to improve the distance
T (°C)
I (nA)
25
80
45
5000
70
14000
60
2500
40000
50
550
30000
40
145
30
45
10000
80
35000
100
70000
0
75
3500
64
1200
48
204
39
566
80000
70000
60000
I(nA)
50000
20000
25
45
70
60
50
40
30
80
100
75
64
48
39
T(°C)
6
HV distributors
o Can solve the 48-32 multiplicity problem removing 1 PCB as suggested
by Riccardo
o From a first by eye inspection of the boards:
- Seems not feasible to change the HV range (500 V) due to
insufficient isolation in PCB
- Seems possible to switch off an entire board (16ch) to be studied
o To change the specifications need to project a new PCB
o No news concerning the connectors and cabling
7
Improving divider performance
8
PMT test station setup
 We built a LED based setup to test the tube performance
– CAMAC driver to control LED light injection
• 0-20V in input to LED 10-400 ns wdt in input to the LED
– Automatic amplitude scan (0.1 V steps) at fixed width (10 ns)
• LED pulses shorter wrt intrinsic LED time constant
• Able to scan the entire QDC dynamics
– Automatic start of Daq acquisition program
• Readout of both QDC (dual range) and TDC
• For each channel 2 different threshold are red out
• Monitor of the LED emission current (new)
– Still to implement automatic HV control
9
Test beam results
For big signals a step in the ToT
distribution is observed
The step is due to the ringing
overcoming the threshold
thr
ToT
10
Il ringing del segnale analogico
L’oscillazione dipende dall’induttanza
parassita degli ultimi 3 dinodi e
l’anodo, causata dalla distanza tra
partitore dinodo!
The “shoulder” is due to a low value of
the C3 capacitor.
11
Correct dynodes effect
To correct the effect due dynodes d10 d11 d12 inductance the quenching
coefficient must be increased:
Cut the routes to d10, d11, d12
Insert one smd resistance on each route
Ad a capacitor in parallel to C3
Ripregnare il PCB
12
Tube performance after dynodes quenching
Same PMT @ 1250V
L’oscillazione e’ sparita come previsto ma
resta la spalla dovuta al fatto che i
condensatori non sono ancora del valore
esatto e risulta necessario inserire una
resistenza
anche
sull’anodo.
La correzione di questo effetto va ad
intaccare l’RC del circuito quindi il tempo
di salita del segnale risulta percio’ piu’
delicata
Le conseguenze della spalla sulla misura di
TOT sono di minor importanza ??
13
Layout of new PCB for LAV PMTs
was 220 V
First dynode clamp (from 220V to 280V)
Quenching of d10 d11 d12 and anode
Quenching capacitor
14
Dynamic range result
Original PMT (75 pC)
Dynode quench(170 PC)
Full modification
Sensitivity region enhanced by
factor near to 10
15
Residual problem
Residual effect 3% of the
16
Conclusion
 The DB37 solution for the flanges is finalized
− No problems for the ANTI-A1,A5
− Density on cables in the vacuum side to be evaluated
for the ANTI-A6,A11
− Option with 2x10 connectors flanges feasible
 The new PCB production for the PMT seems
mandatory
– Improves the ToT by enlarging the sensitive region
– Modify the present PCB requires too much work
– Modify 10 components in the PCB is not feasible
17