Update on ElectronicsActivities

Jim PilcherUniversity of Chicago

20-Jan-2006

January 20, 2006 J. Pilcher2

Readout Electronics

Last talk on electronics was some time ago

Need update on recent activities at Chicago PMT testing R&D on readout Prototype tank being prepared

Recall electronics parameter list on web site http://hep.uchicago.edu/~pilcher/th13/electronics/electronics.html

Active Excel file which will update if input assumptions are changed

Also earlier electronics talk on web site

January 20, 2006 J. Pilcher3

PMT Testing The prototype tank being prepared will use six 8-inch PMTs

More details on tank later in the talk We have 2 from each of three vendors

Candidate tubes for final detector Hamamatsu R5912

– 10 stages, G=107 @ 1500V, dark count rate 4.0 KHz

Photonis XP1806– 11 stages, G=107 @ 1340V, dark count rate 1.6 KHz

Electron Tubes 9354KFLB– 12 stages, G=107 @ 1300V, dark count rate 4.0 KHz

All have low activity glass envelope All equipped with manufacturers’ bases

January 20, 2006 J. Pilcher4

PMT Testing Testing to date is limited

Have looked mainly at single pe pulse shapes

Impacts readout electronics Have looked with illumination of full photocathode and of a 2 cm x 2 cm region

Have operated at HV for G = 107

Measurements also underway in low background lab on activity of glass

Will be reported at future meeting Test with small beaker (~ 200 ml) of liquid scintillator and Co-60 source in a dark box

January 20, 2006 J. Pilcher5

PMT Testing Single pe pulse

from Hamamatsu shows reflection ~10 ns after primary peak

Not scope connection

Multiple pe signal includes scintillator properties

Hamamatsu R5912 - single pe

-120

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0

20

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Time (ns)

Voltage (mV)

FWHM = 5.0 ns

t_rise = 3.4 ns

t_fall = 3.7 ns

Hamamatsu R5912 - multiple pe

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0

100

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Time (ns)

Voltage (mV)

FWHM = 12.8 ns

t_rise = 5.2 ns

t_fall = 15.0 ns

January 20, 2006 J. Pilcher6

PMT Testing Photonis tube

showed low gain and broad signal

Perhaps faulty Need to test

second tube

Electron Tubes tube is similar to Hamamatsu but slightly slower

Photonis XP1806 - all pulses

-250

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0

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Time (ns)

Voltage (mV)

FWHM = 13.7 ns t_rise = 10.8 ns t_fall = 21.1 ns

Electron Tubes 9354KFLB - single pe

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0

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Time (ns)

Voltage (mV)

FWHM = 6.0 nst_rise = 5.7 nst_fall = 13.8 ns

January 20, 2006 J. Pilcher7

PMT Testing Much more work to be done on PMTs

Suggestions and/or visitors welcome No special hardware on hand for detailed measurements

Photocathode uniformity, linearity, quantum efficiency, gain, after-pulsing, magnetic field sensitivity, etc.

Our goal was to take a first look before using them in prototype tank

We would be happy to have help from others on PMTs

January 20, 2006 J. Pilcher8

Readout R&D Strawman proposal presented in earlier talk on web site Dual range, 12-bit readout on each PMT

Gain ratio 32:1 between two scales Separate ADCs on each scale for easy inter-calibration of scales

Overall dynamic range 17 bits 15 counts/pe at low end of range High end ~70 times most probable single muon signal for “average” PMT

PMTs close to muon will receive much larger signals

High energy radiative tail for muons Multiple muons from cosmics Suitability to be confirmed by Monte Carlo studies

January 20, 2006 J. Pilcher9

Readout R&D Design features of strawman approach

Similar to readout approach in ATL AS Tile Calorimeter, Auger, Quiet, …

Convert PMT signal to a pulse of standard shape but amplitude proportional to input charge

Create Gaussian shape with FWHM of 30 ns Sample with commercial 12-bit ADCs every 15 ns. Extract amplitude and time of signal with respect to sampling clock by digital signal processing

Can give sub-1% amplitude resolution and ns time resolution (seen in ATLAS)

Shaper and pre-amp on PMT base Digitizer in VME crate outside containment sphere

January 20, 2006 J. Pilcher10

Readout R&D Shaping obtained with purely passive components (LC) Exploits current source nature of PMT Linearity guaranteed Very low noise Insensitive to input shape Follow with active preamp and line driver

PMTPreampand

Line Driver

January 20, 2006 J. Pilcher11

Readout R&D Packaging and system planning

Shaper on PMT Perhaps on same PCB as voltage divider

Two shielded twisted pair outputs Digitizer on VME board

32 channels per board Form local trigger information from patch of 32 PMTs– Total number of pe

Overall trigger could be based on trigger info from 32 patches

Would allow some geometrical requirements as well as total signal

Trigger could be based on same data as read out

January 20, 2006 J. Pilcher12

Readout R&D Digitize waveform from PMT/shaper every 15 ns

DSP processing extracts amplitude and time Shape below is SPICE simulation of shaper

January 20, 2006 J. Pilcher13

Readout R&D Possible organization

VME Modules

January 20, 2006 J. Pilcher14

Readout R&D Status

Working on shaper design Thinking about VME board

How do we prove this will do the job? Prototype tank already being prepared

Record data with calibration sources Use proposed shaper but commercial digitizer

A CAEN VME module can sample every 0.5 ns Can sample PMT directly to show ultimate time resolution

Can sample shaped signal every 15 ns to show time resolution and performance of shaped scheme

January 20, 2006 J. Pilcher15

Readout Electronics CAEN V1729 VME digitizer for prototype tests• Bandwidth 300 MHz

• Up to 2 GHz sampling rate into storage caps.

• 12 bit A-to-D conversion after trigger

• Memory with 2520 samples per channel

A trigger stops the continuous sampling

• 4 differential inputs per module (2 PMTs)

• 16-bit dynamic range using high-gain and low-gain inputs from each PMT

11 bits reading PMT directly• $2.2K / channel (very pricey!)• 3 modules on order

January 20, 2006 J. Pilcher16

Readout R&D How might electronics design evolve? We have a strawman proposal for front-end and organization

Other options should be considered too Cost and performance important metrics

Alternative readout schemes could be tried with prototype tank

Visitors welcome Many important electronics topics need work

Trigger, signal processing, LV system, HV system, DAQ system

January 20, 2006 J. Pilcher17

Prototype tank Geometry?

~ 1.6 m3 normal liquid scint.

~ 4.4 ℓ Gd loaded scint. In acrylic sphere Movable along axis of cylinder

3 PMTs on each end

January 20, 2006 J. Pilcher18

Prototype tank Plan is to run with various sources and cosmic muons

Californium– a fission source giving prompt gammas plus delayed gammas

from neutrons capture in Gd

Co-60 for photons Validate Monte Carlo code

Tank has different geometry but most of the physics processes of the full detector

Validate readout electronics Get experience with candidate PMTs Test bed for candidate readout systems

Status Tank being fabricated and expected in early February

Three CAEN V1729 modules on order A senior thesis project for Abby so data is needed by May

January 20, 2006 J. Pilcher19

Conclusions That’s it from Chicago!