1. Tile Upgrade Workshop (CERN- February 2008 8 and 9)
On Detector electronics: PMT HV system
Tile Upgrade Workshop (CERN- February and 9)
François Vazeille
Reminder about the Tilecal set-up
Design, production and tests (Clermont-Ferrand)
 Specifications and performances
Reminder about safety factors on radiation effects
Possible improvements

2. Reminder about the Tilecal set-up
… and about the individual regulation loop
Tilecal in-situ regulation
Based on one
Optocoupler chip/channel
Use of an external HV
(common to 24 Channels)
located in USA15 room
HV out
Opto
coupler
From
DAC
Loop working stand-alone
once the DAC value is set
by the user
via the DCS
(…even though
the DCS is lost
or if the HV Micro is dead)
From
HV Source

3. HV Distributors of Super-Drawer
… and about the general set-up in the pit
 2 main elements:
- HV Source (USA15)
- HV Distributors (UX15)
USA15
LVCAN PC HV PC
+ Associated elements and connections:
- CANbus and LVCAN PS (and LVCAN PC)
- DCS: HV PC + CAN interfaces
- fLVPS HV
Source
LVCAN
Patch P
Internal HV Bus
Flex Bus
External HV bus
Long
cable
Internal
HV Opto
External
HV Opto HV
Micro
fLVPS
Short
cable
HV Distributors of Super-Drawer
(6 cards/Super-Drawer)
Daisy
chain
Comment: LVCAN Power Supplies separated for HV and the Integrator ADC
It is an advantage for me because the 2 systems are very different.

4. HV Distributors 5 types of cards
- Bus cards: Stiff Internal, Stiff External, Flexible
- Opto cards (Optocouplers)
- Micro cards (Microcontrollers)
The Microcontroller (MC68376) plays 2 roles:
- Control of the Opto and Micro cards
- CANbus Interface (with a LV regulator powered by a CANbus PS)
Bus cards:
270 Stiff Internal
270 Flexible
270 Stiff External
90x1310 mm2

5. Specifications and performances
110x600 mm2
100x170 mm2
540 Opto cards + other spares
270 Micro cards + other spares
+ Making and use of dedicated Test Benches for each type of cards,
several times used before, during and after burn-in + Drawers Test Benches
+ In particular: Very Long Term Test of Opto cards (Full Daisy chain)
associating HV Distributors and HV Source
Specifications and performances
Specifications: (HV) < 0.5 V in order to have G/G < 0.5% on PMTs
Performances: (HV) < 0.1V from Clermont-Fd, Test Beam and Pit results
Comment: some induced noise on the readout.
Proper to any HV system and due to the whole front-end scheme
but that does not mean that improvements could not be made in the future.

6. Reminder about safety factors
on radiation effects
 Studies (Tilecal notes) made about:
- TID and NIEL doses on cmos and bipolar components
- SEE
TID: Total Ionizing Dose
NIEL: Non Ionizing Energy Loss
SEE: Single Event Effect
ATLAS rules on safety factors
Items
Simulation
uncertainty
Inhomogeneous batches
Bipolar components
Total:
Bipolar
- cmos
TID
3.5 4 5
70 Bipolar
14 Cmos
NIEL 20
SEE

7. We will consider 3 steps: - Nominal Luminosity: 1034
- Ultimate Luminosity:
- Ultimate SLHC:
Tables of safety factors as requested
and as measured (worst location),
for 5 years running in each scenario
 TID
Components
Required
Safety factor
Nominal
luminosity
Ultimate
SLC
HV Micro bipolar
HV Micro cmos 70 14
352
153 35
HV Opto bipolar
HV Opto cmos
318
138 32
- For the HV Opto: it affects generally 1 channel only.
- New tests for bipolar could be requested if the required safety stays at 70,
because of the large uncertainty on simulations (Factor 3.5)
The first ATLAS radiation results will bring useful information.

8. Quoted in parenthesis: pre-prod components
 NIEL
Components
Required
Safety factor
Nominal
luminosity
Ultimate
SLC
HV Micro 20
38 (113)
16 (49)
4 (13)
HV Opto
48 (98)
21 (43)
5 (11)
Quoted in parenthesis: pre-prod components
- For the HV Opto: it affects generally 1 channel only.
- New tests could be requested if the required safety stays at 50,
because of the large uncertainty on simulations (Factor 5)
 The first ATLAS radiation results will bring useful information.
 SEE from tests equivalent to 10 years at 1034
- Latch-up effect: on one Micro card inducing Zero voltage/week
 Recovered by a power cycle of the Tilecal affected component
(here the Super-Drawer) once per day (as foreseen for the whole Tilecal)
Comment: 3 SEU per minute in the whole Tilecal
- No destructive SEU during the tests:
What would be the results at a higher luminosity?
 The first ATLAS results will bring useful information,
in particular about the large simulation factor (5).
Conclusion: no so far about radiation effects  First ATLAS results waited.

9. Possible improvements
… always possible once the experience comes at the full scale
from the whole detector …
 Why an in-situ regulation?
To optimize both the regulation close to the channels and the noise effects
(no pick up on very long cables)
+ separation of HV side and readout-side.
- To save money: no equivalent commercial product.
 Possible improvements from the most important to others
The most important: direct link with fLVPS (mainly a hardware link),
in particular in case of a destructive SEU.
- New HVFLEX (already found … but expensive).
- Noise killers integrated in the cards on every channel (HVBus or HVOpto).
Better optimized design of the HV tracks on the HVBus boards
(Possible source of noise).
- Individual switches (And not 1 for 12 channels) … but more expensive.

10. BUT some components would become obsolete if too many things were changed!
Why not taking benefit of Micro-electronics?
Why not using rad-hard components? But cost!
 Are there alternative solutions?
- Everything in the counting room?
Come back to the starting point:
- Space in USA (Take as reference the volume of Prague HV Source)
long cables
- Noise problems
- Cost if commercial
unless moving the present HV Distributors in USA15 ? …
- Everything in the cavern but outside the Modules?
 The worst solutions: radiations higher than in the Girders.

11. First conclusions We need to know better the whole HV system,
including the HV Source and the fLVPS + the CANbus PS
in order to finalize the specifications of what could be a perfect system.
So we must execute the HV Commissioning as foreseen in the WP10
possibly by revising it (My job in the next weeks).
We are not very far from what would be needed at the radiation level
and the ATLAS running will provide very useful information on:
- The true radiation levels  Safety factors revised.
- The behavior of the HV system.
 New radiation tests will be likely requested.
It is not clear that an upgrade should be needed,
even though some weak points would stay.
 A medium solution could be a smooth upgrade: the most important points,
without remaking everything, saving time and money.