essd2005 - Particle Physics

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Transcript essd2005 - Particle Physics

10th European Symposium
on Semiconductor Detectors
The Backward Silicon Tracker
Applications:
Heavy Flavor Physics
Inelastic eP-scattering cross-section:
• Track trigger for an efficient use
of the high luminosity of HERA-II
The New Radiation-hard Readout
for the Forward and Backward
Silicon Detectors of H1
DIS Measurements with the BST

 σ(x, Q ) 2s2

 F2 (x, Q 2 )  y 2 FL (x, Q 2 )
2
4
2
2
xQ
• Track curvature measurement and the
particle’s momentum determination
xQ
Acceptance for
heavy quarks with
the FST and BST
Q2 ~ (5…400 ) GeV2

BST acceptance in the
x, Q2 kinematical plane
• Z-vertex reconstruction and
rejection of non-eP tracks
and other background
Event kinematics:
I.Tsurin
Q 2   q 2  (k  k' ) 2  4 E e E' e cos 2 ( / 2);
E'
P q
y
 1  e sin 2 ( / 2);
Pk
Ee
University of Antwerpen,
on behalf of DESY
x
Q2
;
sy
Deeply Inelastic Scattering event
Strip detector
(640 readout strips)
Pad detector
(32 pads)
Inclusive measurements
of a scattered electron with
a calorimeter and the BST:
Address: Notkestrasse 85,
22607 Hamburg, Germany.
E-mail: [email protected]
Detector system
Phone: +49-40-8998-4598
• 144 strip detectors
(number of readout
channels = 92.160)
Wildbad Kreuth
June 12-16, 2005
• 48 pad detectors
(number of trigger
channels = 1536)
Detectors Assembly
The new “Analog Pipeline Chip”
Strip Detector Module
The APC128 readout chip and its decoder were re-designed in
collaboration between DESY, PSI (Villigen, Switzerland) and KIP
(Heidelberg, Germany) and manufactured in 0.25 um process by
UMC (Taiwan).
Strip detectors
F2c
measurements (2…10)%
in extended x range
F2b
measurements with
high luminosity
Preamplifier’s Circuitry
Ring-shaped P-FET from the
“PSI_025V2_core” library
P-FET transistors enclosed in
the N-well are better isolated
from the P-substrate leakage
currents. Their usage in the
preamplifier’s feedback circuitry requires negative bias
voltages with respect to the
signal ground.
To prevent high stress current
density during plasma exposure
the gate voltage must be always
above the substrate potential *
The strip pitch = 25 µm, the readout pitch = 75 µm (every third strip has an
analog readout). The charge sharing between intermediate and readout strips
allows for a precise coordinate measurement: hit residuals for tracks 10-15 µm.
A serial readout of two detectors (2 x 640) strips with 1 µs / channel requires
1.3 ms for the data processing with a continuously cycling acquisition program
(sequencer code). The APC settings are reloaded regularly making the readout
rather stable against single event upsets.
Pad detectors
The old APC128 SACMOS radiation damage studies*
A cumulative dose above 100 kRad is responsible for the pedestal and hence
readout amplitude lowering. This effect is attributed to the bulk leakage current
at the preamplifier's input. The influence of impurities trapped in the silicon onto
signal could be parameterized and investigated in the ASIC design package with
an equivalent current source.
Front-end functions (less critical to the choice of components):
Signal buffering, Clock distribution, Supply regeneration
* “Development of a radiation hard version of the Analog Pipeline Chip
APC128”, M. Hilgers, R. Horisberger, Nucl. Instr. Meth. NIM A481 (2002)
pp. 556-565.
Pad Detector Module
Pad Front-end Electronics
APC128 UMC.25 specifications:
• 128 channels, each containing an analog pipeline with a depth of
32 storage capacitors
• ENC (1σ) 400±100 e (the switching noise has a large contribution)
• Shaping time constant 1.5±0.3 µs
• Minimum sensitivity 5±1 mV/fC; the signal amplification and
processing is possible by sequencer code
The online Trigger Software
Single event upset may force a trigger signal. The coincidence with other
H1 sub-detectors (SPACAL, Veto counters etc.) reduces a risk of a
false trigger. All signal conditions and relations are synchronized to
the clock frequency to protect the trigger algorithm against random
data changes .
Memory bit flips were crucial for the frequent trigger masks, therefore the
predefined track patterns were coded as combinatorial logics.
Single event latch-up can freeze data bits distorting the trigger patterns.
A self-latch scheme for input signals with a common reset is utilized
to avoid combinations with permanent "1". Mask permutations are
written to compensate for stuck signals or inefficient pads.
The front-end boards for the detector control and the trigger data
processing (ALTERA chip EP20K300E is the core of each board):
PRO/A readout chip
Specifications:
• Manipulating the PRO/A steering codes, setting trigger thresholds
• Synchronization of all detector pulses to HERA clock frequency
• Track validation with masks and computing of the track topology
• Accumulating and transmitting of raw data from the silicon pads
• 32 channels with digital and
analog outputs with controlled
ON / OFF function and internal
or external trigger thresholds
• Dynamic input range 35±1 dB
• Controlled gain 15…30 mV / fC
• ENC (1σ) 600±100 e
• Noise slope 15±5 e / pF
• Shaping time constant 30±1 ns
• Has a calibration pulse mode
96 channels
• Temperature
measurements
with a CAN chip.
Radiation Background
Radiation Monitor for H1
Intense background components:
• Synchrotron radiation:
The synchrotron radiation fan
does not enter the H1 facility
directly but some part of it
scatters from absorbers towards the detector and does
heat the beam line optics that
causes a gas evaporation and
worsens the vacuum. In turn
this increases a
Soft failures are resolved by the front-end reinitializing
Radiation Monitor for HERA
The radiation monitor rate depends
on the vacuum in HERA, therefore for
the given conditions the background
can be predicted in the first approximation from the current product:
Reaction to the beam currents
Dose rate measurement with Pads
The trigger algorithm of the pad detector was extended to monitor online
the particle flux through the silicon. The multiplicities of triggered pads are
summed up within 1 second, during the next second the result obtained is
sent out while the next integral is being prepared.
One silicon sensor (20 cm2)
is taken as an area unit for
the radiation monitor. The
maximum rate over 48 pad
detector modules is being
displayed.
FST and BST Collaboration
• DESY Zeuthen
• DESY Hamburg
• Prague Charles University
• Institute of Physics AS CR
• Rutherford Appleton
Laboratory
dN
 I p(P0  αI e )  α I p  I e
dt
Detector Smiths
• e-gas scattering
• P-gas scattering
where the latter is the main
background component.
• Field programmable gate arrays (ALTERA):
EP20K300EQC240, EP1K30TC144
• Fast comparators (MAXIM): MAX964EEE
• Opto-couplers (Agilent): HCPL-0731
• Low dropout voltage regulators (Nat. Semicond.):
LM3965ES, LM2991S, LM1117MP, LM1086CS
• Amplifiers (Analog Devices): AD8554AR
• Reference (Analog Devices): AD589JR
• Differential transmitters / receivers (Texas):
AM26LV31CD, AM26LV32CD
3. To ensure a reliable operation in the environment with radiation
load a steady HERA background control and a fast response on
radiation effects in the silicon are very important to keep the
exposure rate below 10 kRad/year.
Auxiliary functions:
The PRO/A readout chip was designed in collaboration
between DESY Zeuthen and IDE AS (Oslo, Norway) and
manufactured in 1.2 µm N-well CMOS process by AMS.
Commercial components preserving general
functionality with the total ionizing dose up
to 3.2 MRad:
2. As much functionality as possible should be implemented into the
program algorithm. It is always easier to recompile the design activating new FPGA resources than to repair the hardware.
Interface to
the H1 DAQ
384 channels
Design Outlook
1. Analog circuits should have 100% feedback, i.e. voltage repeaters
must be used rather than amplifiers. In any case the digital circuitry
is preferable because it operates with two robust levels.
• Monitoring the radiation
background
Detector
Modules
* “Plasma-charging damage in ultra-thin gate oxide”, Kin P. Cheung,
Microelectronics Reliability 40 (2000), pp. 1981-1986.
Operation experience:
• Monitoring the multiplicity
of triggered pads
• Individual mode / subtraction
of neighboring channels for the
common mode suppression
The signal ground is separated from the substrate and the operating (.)
of the push-pull cascade is shifted by +0.6 V. Now the gate voltage of
the feedback transistors could be selected in the range (0…+0.6) V.
A linear correlation between the radiation
monitor rate and the ionization current in
the central trackers is used for chambers
to control their “turn on” conditions to
prevent their high voltage trips.
The instantaneous count rate can be helpful for the HERA crew as a
feedback from the detector during injection and the beam steering:
http://h1lumiserver.desy.de:8080/main/h1mon.html
In coincidence with some other counters the radiation monitor can be
used for an automatic beam dump in a case of severe radiation load.
Correlation with scintillation counter rates
Measuring the cumulative dose
becomes possible with silicon
detectors (besides beam losses
when the energy is released in a
very short time) as all particles
deposit on average the same
2
energy   2 MeV cm / g
D  N (counts) 

S[cm2 ]
Max Klein  Peter Kostka  Thomas Naumann
Jan Kretzschmar  Tomas Lastovicka  Mirek Nozicka
Wolfgang Lange  Hans Henschel  Joachim Meiβner
Rainer Wallny  Doris Eckstein  Vladimir Arkadov
Milan Janata  Ulrich Harder  Wolfgang Eick
Wolfgang Philipp  Olaf Gräber  Ilya Tsurin
Sergey Gorbunov  Bill Haynes  H.-C.S-C.