1 some high rate measurements at IC Mark Raymond m.raymond@imperial.ac.uk attempt to re-produce CERN...

1

some high rate measurements at IC

Mark Raymondm.raymond@imperial.ac.uk

attempt to re-produce CERN high-rate behaviour in the lab at IC

a few new (I think) observations

CMS readout chain (transmission/FED system) can be ruled out

module (hybrid) without sensor does not show problem

2

setup

UTRI cardLV regs,interface buffers

CK/T1

I2C

CK/T1 and I2C provided bycustom VME modules (no CCU)

SeqSi digitalpattern

generator

triggerveto

outputdata stream

ADC, 128kdeep memory

digitalheaderdetect

count up

count down

trigger veto using simple counterincrements on scintillator triggerdecrements as APV frames outputveto if count reaches 9 (safety margin)

source

PM/scint.

front end

experimental techniquefree run system with random triggerstrigger and readout all 128k ADC samples(accommodates ~ 300 data frames at ~ 100 kHz)repeat to build up larger data setsanalyse data

source generatesrandom triggers

3

reproduction of effect on TEC module70

60

50

40

30

20

10

0

rms

AD

C u

nits

250200150100500channel number

TEC module, ~20 kHz random triggers

70

60

50

40

30

20

10

0

rms

AD

C u

nits

250200150100500

channel number

TEC module, ~100 kHz random triggers

noise dependence on channel number

(couple of bad channels)

noise increases with trigger rate

readout interface completely differentto CMS system => problem confined to front end module

chip 1 chip 2

4

effect on TIB hybrid only25

20

15

10

5

0

rms

AD

C u

nits

250200150100500

channel number

TIB hybrid only, ~20 kHz random triggers

25

20

15

10

5

0

rms

AD

C u

nits

250200150100500

channel number

TIB hybrid only, ~100 kHz random triggers

no sensor

noise unaffected by trigger rate

=> sensor necessary to reproduce effect?

maybe but TIB hybrid layout slightly different to TEC

=> look at TIB module

chip 1 chip 2

5

reproduction of effect on TIB module

70

60

50

40

30

20

10

0

rms

AD

C u

nits

250200150100500

channel number

TIB module, ~ 20 kHz random triggers

70

60

50

40

30

20

10

0

rms

AD

C u

nits

250200150100500

channel number

TIB module, ~ 100 kHz random triggers

effect also reproducible in TIB module

=> confirms sensor required

(some bad channels on this module too)

chip 1 chip 2

6

problem data frames

-300

-200

-100

0

100

200

300

AD

C u

nits

250200150100500

channel number

-300

-200

-100

0

100

200

300

AD

C u

nits

250200150100500

channel number

some “bad” examples

note anti-correlation between

chip 1/ch127 and chip 2/ch 0

chip 1 chip 2

7

coupling speculation

GND

V250

GND seems to be only terminal in the right place?

disturbance on GND would couple more strongly to

chip 1, chan 127, 127, 125, ….. than to chip 2, chan 0, 1, …

weak coupling here

stronger coupling here?

but …

anti-phase ch127chip1/ch0chip2 doesn’t makesense to me

maybe this is misleading …

chip 2

chip 1

127

0

PA

8

coupling speculation …

…. maybe this is misleading

chip 2/ch0 noise might still be there even if chip 1 not there

could confirm by removing power to chip 1

would have to pull bonds to stop all chip 1 digital functionality bit drastic but maybe worth doing?

-300

-200

-100

0

100

200

300

AD

C u

nits

250200150100500

channel number

put it another way

would chip 2 effect still look like this without chip 1

chip 1 chip 2

9

observations

a worthwhile exercise I think

effect reproduced without conventional CMS readout chain=> front end problem – data transmission/FED system not implicated

effect not seen on hybrid alone=> sensor presence is required

shape of effect (data frames) is strange – per APV rather than per hybrid=> APV is somehow implicated?

10

extra

11

APV picture

12

APV pads

13

APV front end

14

APV back end