Status of the MaPMT o Status quo o Ongoing work o Issues – mechanics – electronics – schedule...

Status of the Status of the MaPMTMaPMT

Status of the Status of the MaPMTMaPMT

Status quo Ongoing work Issues

– mechanics

– electronics

– schedule Conclusions

LHCb meetingMilano 26. 9. 2000

Franz MuheimUniversity of

Edinburgh

Milano, 26. 9. 2000 LHCb RICH meeting 2

Status Quo Status Quo

Successful test of 3x3 array of MaPMTs– Quartz lenses and close packing work – Measured photon yield as expected– Demonstrated 40 MHz read-out with APVm chip

MaPMT works in LHCb environment– charged particles traversing lens and photocathode– magnetic field

MaPMT fulfills LHCb RICH requirements Front-end electronics needs to be optimised


Photo Detector DecisionPhoto Detector Decision

Pixel HPD is baseline– must fulfill milestones

assessed at the end of 2000 MaPMT is backup Keep the MaPMT viable until end 2000 recommended work programme

– F/E readout: SCT128A – gain matching

Attenuators or reduced gain of MaPMT final decision: end 2000


ImprovementsImprovements

Further improvements possible– 3-5 % higher QE is possible (manufacturer)

14-23 % more photons– Incorporate lens into vessel window

8% more photons– Optical coupling between lens & MAPMT

8% more photons– Binary electronics

Cost savings– Use 4 threshold cut

Smaller signal loss


Laboratory Results Laboratory Results

Pixel scan with LED

Signal / pedestal = 40:1 Signal loss below 5 cut: 11.5 %

Single channel spectrum (LED)

-900 V

Better focusing improves collection efficiency


Low GainLow Gain

Dynode Chain

3

2 2

1 1 1 1 1 1 1 1 1

5

4

2 2

1 1 1 1 1 1 1 1 1

5

4

3 3

1 1 1 1 1 1 1 1 1

50

1

2

3

4

5

6

1 2 3 4 5 6 7 8 9

10

11

12

An

od

e

Dynode

Res

ista

nce

[10

0 kO

hm

]

default medium gain low gain

Additional studies with better sensitivity needed

Looks promising


MechanicsMechanics In good shape

– for the photo detector decision 12/99

MAPMT pitch: 26.7 mm Module pitch: 108.8 mm -metal shield: 0.4 mm Mounting frame: carbon

fibre, G10 Have enough time to

finalise design


Front-end ElectronicsFront-end Electronics Options: 4 x 2 (SCTA128 or BEETLE)

all would probably work– preamplifier with lower gain– attenuator network, separate chip or passive– low gain

Preamplifier modification – preferred solution– needs design effort: J. Buytaert & N. Smale

Attenuator network– passive Xtalk?– active decouples preamp, needs design effort

Low gain– increases signal loss, less flexibility


Status of ASICsStatus of ASICs SCTA128A_VELO

– modified backend - 32 MUX– submission delayed Nov 2000 - with CMS – tested march 2001

SCTA “2” used by vertex group and Pad HPD

SCTA “3” production problem, available end Nov Beetle

– arrived at Heidelberg 3 weeks ago– shortcut in buffers prevents programming with I2C try

to fix with ion beam – test structures with low gain

“The results look good and close to simulation” - N. Smale– next submission planned Jan 2001


Binary ReadoutBinary Readout Only with Beetle, SCTA128 is analogue Advantages

– ODE design for Pixel HPD can be taken “asis”

– Optical links and 80 m between F/E and ODE

– Cost

Does it work? HERA-B RICH has MaPMTs with binary readout

Must be studied - before end 2000Estimate signal loss, parameters:– measured signal shape

– mean gain of tube

– spread of gain from pixel to pixel

– collection efficiency within pixel


New ScheduleNew Schedule


DiscussionDiscussion Mechanics ok Front-end chip and mother board on critical path Mother board

– can profit from design studies for the photo detector choice but lots of effort needed

– need motherboard to test MaPMTs 1/2002

Front-end chip– gain matching needs effort and time

– binary read-out has many advantages

– Prefer same choice as vertex detector

– analogue read-out restricts ODE to 12 m, copper links,radiation - single event upsets, same for vertex

detector

– need a functional front-end electronics for 1/2002


ConclusionConclusion Multianode Photomultiplier Tubes are an excellent

backup solution– No primary worries left

Big effort needed for proper Front-end and Off-detector electronics

Front-end chip and mother board on critical path Need a fully committed team and a final decision

should be taken at 12/2000 Backup solutions are only taken serious once the

baseline has failed We cannot afford to delay a decision after 12/2000

without delaying the LHCb RICH project

Status of the MaPMT o Status quo o Ongoing work o Issues – mechanics – electronics – schedule...

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