1. Mr Ángel Perea Martínez
CHAMBER DESIGN APPROACH FOR SILICON
DETECTORS IN EXPERIMENTAL SETUPS
Mr Ángel Perea Martínez
Prof Olof Tengblad
Instituto de Estructura de la materia, CSIC
Instituto de Estructura
de La Materia

2. 1-13
Introduction
Experiments usually involve several (6+) dsssds with 32 channels + other detectors, inside the chamber. Total number of feed-thorugh channels well up to
Angles and distances are important. Usually is difficult to check that the detectors sit in the intended place
Noise reduction is also a main issue.
Traditional solution for feedthrough is use of commercial vacuum conectors.
Preamps and acq-chain
Outside chamber
DSSSD + PAD
telescopes
Incoming beam
target

3. 2-13
Introduction
Connections done with several (one per detector) lemo feedthroughs. Inside the chamber, jacketed flat cables ending in IDL34 or similar connectors
However:
cables prone to shortcuts
Bulky, dangling cables inside (note two lateral flanges dedicated to feedthrough). Extra space implies pumping times
Stiffness of cable maze exerts pressure on etectors → misplacing, bending
Proposed Solution:
We’re developing more compact solutions to bring signals out of the chamber, using standard Printed circuit boards (PCBs)
Two complementary ideas:
Use PCBs as feedthroughs
Use PCBs for detector placement

4. Expected problems 3-13 Impedance:
There is no matched impedance from detector to preamp. 50 Ohms std. starts at the output from the preamp.
Calculations shown that impedance for PCB routes stay in the range Ohms. Std flat cable (S-S mode) is about 120 Ohms
Lenghts: Cables have a distinctive advantage: same length for every channel. At 3 ps/mm.
Typical TDC 128-ch resolution is 100ps (Caen 1190-A )
Other:
Resistance: slightly higher in PCBs
Track corners: problem in prototypes
Routing: need for high-speed routing
Cross-talk: signals are too weak to affect. Distance between tracks similar to std cable pitch (50milis). Experience shows that crosstalk happens in latter stages

5. Simple 2x34 signals Meant to be used as an Std feedthrough
4-13
First prototype
Simple 2x34 signals
Meant to be used as an
Std feedthrough
Proof of concept
Those cards were later used for IS489 at MINIBALL,
In a design involving cryogenics and mag. field, were
space was scarce and material should be kept at minimum

6. Practical setup 5-13 Mechanically:
Needs some suport at both sides to prevent bending: backing metal plate
Needs vacuum sealing: Expect 1Kg/cm2 pressure (keep slit walls rough). Use epoxy sealing (torseal)
Dsssd photoelectric effect. Needs sealing opaque to light: add compatible pigment (Fe203)
Setup alignment will depend on this stage Should be mounted and checked before sealing
Electrically:
Outside the chamber: signals must be shielded (→ extra layers or outer shielding)
Inside the chamber no need for EM shielding. Just isolation

7. 6-13
TRIUMF12 design (1)
In 2012 (and again in 2013) we got beamtime for 11Be and 11Li experiment in Tigress setup at Triumf (Vancouver), sharing beamtime with another group with a different detector geometry.
Handover should be made quickly: ideally, detectors mounted, ready to swap.
We didn't want to make again calibrations, or minimize need for them.
Feedthroughs were fixed by setup.
We went for a design of motherboard plus adapters
We designed and , together with Tharsis technology S.L, built the following setup
Incoming
Beam
Cabling from subtable to flange

8. TRIUMF12 design (2) 7-13 PCB divides chamber space
In two halves. Cables stay
In the lower part.

9. 8-13
TRIUMF13 design (3)
With this setup, pads can be independently calibrated sitting on the same connectors
Subtable + target holder in Tigress setup.

10. TRIUMF12 design (4) 9-13 What we've learnt from it:
Channel mapping is an issue. We had code to get the mapping from the design/gerbers, but it needs too many adjustments and is prone to errors. External swapping occurs (DAQ-dependant) → Devise a way of doing the mapping
Signals up to 400V can be safely routed in the PCB (Connectors used claim up to 1000V). Specially need for pads behind.
Excellent noise-levels, improved resolution.
We experienced again problems with connectors
Alignment is not an issue, provided the previous collimator can be moved. PCBs stay aligned with around 1mm accuracy.

11. 10-13
JYFL13 design
We are currently building the second experimental setup to be used for a 12C experiment
This year(?) at Jyvaskule (Finland). This setup gets rid of cables altogether.
Target-change still
To be determined
Precollimator
To supress beam-halo
Current-measurement
For alignment
(no secondary e- supp.)
Preamps connect
Directly to PCB

12. JYFL13 design 11-13 Table with detectors is plugged from below.
Sideplates take signals out of
The chamber. No cables
ISA connector, from table to
sideplate-PCB.
Two kinds of preamps
Can be used in combination
Mesytec mpr-32 and mpr-64

13. Further Developments 12-13 Testing the Jyfl14 setup
Looking for better routing: GEDA toolchain is notoriously inefficient on routing when connectors sit at angles different from
Trying to find PCB prototypes with competitive prices. Trying to keep designs in 4 layers.
Outsource manufacturing to interested companies. Workshops can’t cope with deadlines and changes. .
Developing demultiplexed 32xN ch. pulser for automatic channel mapping (pulse signature)
Use flexible printed circuits.

14. Thanks for your attention!