1. Update on Electronics Activities
Jim Pilcher
University of Chicago
20-Jan-2006

2. 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
Active Excel file which will update if input assumptions are changed
Also earlier electronics talk on web site
January 20, 2006
J. Pilcher

3. 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, 1500V, dark count rate 4.0 KHz
Photonis XP1806
11 stages, 1340V, dark count rate 1.6 KHz
Electron Tubes 9354KFLB
12 stages, 1300V, dark count rate 4.0 KHz
All have low activity glass envelope
All equipped with manufacturers’ bases
January 20, 2006
J. Pilcher

4. PMT Testing Testing to date is limited
Test with small beaker (~ 200 ml) of liquid scintillator and Co-60 source in a dark box
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
January 20, 2006
J. Pilcher

5. PMT Testing
Single pe pulse from Hamamatsu shows reflection ~10 ns after primary peak
Not scope connection
Multiple pe signal includes scintillator properties
January 20, 2006
J. Pilcher

6. 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
January 20, 2006
J. Pilcher

7. PMT Testing Much more work to be done on PMTs
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
Visitors and/or suggestions welcome
January 20, 2006
J. Pilcher

8. R&D on Readout 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. Pilcher

9. R&D on Readout Design features of strawman approach
Similar to readout approach in ATL AS Tile Calorimeter, Auger, …
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. Pilcher

10. R&D on Readout 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 linear line driver
Preamp
and
Line Driver
PMT
January 20, 2006
J. Pilcher

11. R&D on Readout 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. Pilcher

12. R&D on Readout 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. Pilcher

13. R&D on Readout Possible organization VME Modules January 20, 2006
J. Pilcher

14. R&D on Readout Status How do we prove this will do the job?
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 1.0 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. Pilcher

15. R&D on Readout 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. Pilcher

16. R&D on Readout 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. Pilcher

17. Prototype tank Geometry? ~ 1.6 m3 normal liquid scint.
~ 4.4 ℓ Gd loaded scint.
In 10-cm radius acrylic sphere
Capture length ~ 4 0.2%Gd
Movable along axis of cylinder
3 PMTs on each end
January 20, 2006
J. Pilcher

18. 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 Kaboth so data is needed by May
January 20, 2006
J. Pilcher

19. Conclusions
That’s it from Chicago!
January 20, 2006
J. Pilcher