Dubna, Russia, JINRLPP I'Boguslavsky, V'Bychkov, Ju'Gusakov, N'Grigalashvili, G'Kekelidze, K'Leverto

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CBM STRAW TRANSITION RADIATION DETECTOR/TRACKER
(TRT)
Dubna, Russia, JINR-LPP


I.Boguslavsky, V.Bychkov, Ju.Gusakov,
N.Grigalashvili, G.Kekelidze, K.Levertov,
V.Lucenko, V.Lysan, V.Mialkovski, S.Mishin,
S.Parzhicki, D.Peshekhonov, V.Peshekhonov,
O.Strekalovskiy, K.Viriasov, Ju.Zlobin Gatchina,
Russia, PNPI


A.Nadtochii, Y.Riabov, D.Seliverstov  
Juelich, Germany

P.Wintz
Moscow, L.I. of Ph., Russia





V.Tikhomirov Rossendorf FZ, Germany,



L.Naumann  Warsaw, Poland, University of
Technology

K.Zaremba, J.Marzec
V.Peshekhonov
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03.10.2004
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CBM STRAW TRT
Target-Detector distance 1-st module - 4
m 2-d - 6 m 3-d
- 8 m Angle Acceptance
from 50 mrad to 500 mrad
Sensitive area X(horizontal) x Y(vertical) for
1-st, 2-d, 3-d module
(5.8 x 3.9) m2 (8.7 x 5.8) m2 (11.6 x 7.7)
m2 Space Resolution - lt 200 µm Rejection of
electrons from pions 300 Counting Rate -
to 10Mhz/channel
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CBM STRAW TRT
Why straws? 1. Good time, space and energy
resolution 2. Small radiation length 3.
Small own noise of the detector gas volume (cmp
to DC) 4. Good aging properties 5. High
rate 6. High ratio of the sensitive area to the
overall dimension 7. High technological
detector, the big contribution of enterprises on
the detector building 8. Presence
completed R_at_ D and the experience of the big
systems creation The 7-th and 8-th points should
help on the detector and its readout creation and
save some time and money
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CBM STRAW TRT
TRD SYSTEM CONSISTS of 3 MODULES
MODULE CONTAINS the X, U and V TWO-LAYER
PLANES (SUBMODULES) with vertical
orientation of straws, inclined on 10 and 10
degrees AND 6 RADIATOR STACKS (one per each
straw layer) THICKNESS OF
MODULE IS ABOUT 60 cm
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CBM STRAW TRT
Submodule - Different size 2-layer straw
chambers are mounted into the carbon structure of
the submodule

• Support frame
  To provide an external protection and to make a
  monolithic two layer submodule
  To provide the high accuracy
  of the chambers installation in the structure (
  100 µm) and high stability of the position
  To align all chambers together
  To ex?lude any dependence of
  the chamber positions on the temperature and
  humidity
• Main requirements to the frame and subframes
• high stiffness and long term stability
• the gaps between the subframes,

Submodule
Y
X
used to pass chamber services and front-end
cards, should be minimized
V.Peshekhonov
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03.10.2004
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CBM STRAW TRT
Two layer straw chamber
beam
1-st layer of straws is shifted to the 2-d straw
layer by one straw radius
STRAW the basic detecting element of the TRT is
made from a loaded kapton XC type with the
resistivity of 380 O/Sq (for anode readout) or of
100 kO/Sq (for the anode and cathode
readouts) Thickness of the straw wall 60
µm STRAWS are glued in planes. The cylindricity
of each straw is better 100 µm. ANODE WIRES - 30
µm Tungsten Rhenium Wires with 3Au are under HV.
Tension - 70g.

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03.10.2004
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CBM STRAW TRT
To increase the straw rate capability, the anode
can be divided into two independent parts (left
right)
Right anode wire
To amplifier 1
To 2
Left anode wire
The glass capillary tube is used for the
glass-joint
Other diameter 0.25 mm Inner diameter 0.1
mm Weight 0.19 mg
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03.10.2004
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CBM STRAW TRT
L 5 mm
Straightness is better 50 µm
L 6 mm

Wire-joint production station in Dubna with a
microscope and TV control system
V.Peshekhonov
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03.10.04
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CBM STRAW TRT

MECHANICAL COMPONENTS End-plugs, spacers
moulded by polycarbonate Wire crimping tubes
Cu, outer/inner diameter 0.7/0.1 mm, length
7mm RADIATORS Thickness 3 cm
15 µm thick polypropylene foils.
Spacing between foils 200 µm SUBFRAMES

WEBs OF ANODE READOUT
Carbon fiber bars with a very high thermal
conductivity. Each one contains gas manifold and
provides the fixation of the radiator,
electronic boards etc.
STRAW PLANE
Two thin Al bars - to provide the equal
temperature elongation of the bars and the
straws. The bars have precise holes for
positioning of the chamber in the structure.
WEBS OF ANODE READOUT
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03.10.2004
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CBM STRAW TRT
To correct the timing information for the anode
signals along the straws the cathode strip/pad
readout can be used
FILM READOUT PLANE ONTO THE BACK SIDE OF THE
STRAW PLANES CAN BE PLACED Resistivity of the
straw cathode should be 100 kO/sq
STRAW PLANE

Rate capability should be checked
( Cathode readout can be used for the coordinate
measurements. Space resolution will be 100µm.
Readout plane is more closely to the anode plane
in cmp to Drift chamber - less area for the
inductive signals )
V.Peshekhonov
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03.10.2004
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CBM STRAW TRT
Operating GAS MIXTURE - XeCO2 (75/25) ArCO2
(70/30) for testing of max drift time value
for different size straws
Uniform irradiation of the straws
Gas gain 2 x 104
Atlas experience for 36 864 straws with 42cm
length ?A/A lt 5 - 93.74 lt 9 - 99.63
17lt0.06 gt 9
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03.10.2004
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CBM STRAW TRT
STRAW the basic detecting element of the TRT
Effective gas thickness of straw
One module containes 6 straw layers
XeCO2 - 75/25
The cluster count method can be used N should
be gt 3
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03.10.2004
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CBM STRAW TRT
The hit number for every straw was estimated For
this purpose full area of the straw layer was
divided on the lines with height - h The map of
the maximal numbers of the hits per each cell
with the size (a ? h) was done For 3-d module
h 50 cm straw diameter 6 mm
size of cells - (25 x 50) cm2 size of
beam hole is 66 x 66 cm2 - corresponds to the
emission angle 40 mrad
Histogram for the 1-st layer
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03.10.2004
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CBM STRAW TRT
Number of hits for the 1-st layer near the beam
hole
3-d module
Number of hits in layer 2
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CBM STRAW TRT
Similar maps has been made for each module. It
allowed to define the preliminary sizes of each
chamber The maximal hit density of the charged
particles is 0.2 0.3 events per collision at
25 AGeV and at emission angle near by 50 mrad per
readout channel. (2 3) MHz in cmp with 7
MHz of ATLAS TRT

• Main parameters for the chamber size
  optimization
• limitation of max density of hits per collision
• angulare acceptance closely to 50 mrad
• number of straws should be divisible
  by sixteen
• minimize the insensitive area
• some unification of the chamber sizes for
  submodules

V.Peshekhonov
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03.10.2004
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CBM STRAW TRT
¼ part of submodule for 3-d module
Straw diameter 6 mm Beam pipe diameter - 60
cm Insensitive submodule central area 80 x 80
cm.sq. Angle acceptance from 50 to 500 mrad
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CBM STRAW TRT
Max amount of the hits per readout channel per
collision
(height)
Angulare acceptance 50 mrad
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CBM STRAW TRT
¼ part of submodule for 2-d module
Straw diameter 6 mm (blue straws of 7-th
chamber is 4 mm diameter) Beam pipe diameter -
61 cm Angle acceptance from 50 to 500
mrad Beam pipe diameter should be reduced to 40
cm
4
4
6
630
7-a
4
4
7-b
914
Max occupancy 0.35
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03.10.2004
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CBM STRAW TRT
¼ part of submodule for 1-d module
Straw diameter 4 mm Beam pipe diameter - 40
cm Angle acceptance from 50 to 500 mrad Beam
pipe diameter should be reduced to 20 cm
8-a
8-b
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03.10.2004
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CBM STRAW TRT
Insensitive anode
25
20
Max straw occupancy 0.35-04
V.Peshekhonov
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03.10.2004
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CBM STRAW TRT
NUMBER OF STRAWS AND READOUT CHANNELS
V.Peshekhonov
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CBM STRAW TRT
Simulation of the TRD
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CBM STRAW TRT
Simulation of the TRD
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CBM STRAW TRT
Pion efficiency at 0.9 electron 20 GeV, 4 mm
straw, 15 µm foil thickness, 70 gas mixture
3.6 cm radiator thickness
2.6 cm radiator thickness
1.6 cm radiator thickness
V.Peshekhonov
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03.10.2004
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CBM STRAW TRT
Pion efficiency at 0.9 electron 20 GeV, 4 mm
straw, 70 gas mixture, 2.6 cm radiator thickness
Comparison of the different film thickness for
200 µm gap green color
V.Peshekhonov
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03.10.2004
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CBM STRAW TRT
Pion efficiency at 0.9 electron 20 GeV, 70 gas
mixture, 2.6 cm radiator thickness
4 mm straw
6 mm straw
V.Peshekhonov
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CBM STRAW TRT
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CBM STRAW TRT
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CBM STRAW TRT
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CBM STRAW TRT

• TRT Front-End Electronics
• - FIRST BOARD Amplify the incoming signals,
  Shape, Baseline Restorer, Dual Discriminator
• Input impedanc 270-300 O
• Peaking time 8 ns
• Width of signal at the base 25 ns
• Operating thresholds 2 or 3 fC - (200 or 300)
  eV for LLT
• 60 fc
  6 KeV for HLT
• - Power consumption 30 mW/channel

8-th channels ATLAS ASDBLR chips can be used
- SECOND BOARD Obtaining of the timing
information (TI) for exceeded LLT signals,
Storage the TI and signals exceeded HLT in a
pipeline, Control the ASDBLR, etc DTMROC
New technology with low power consumption can be
used
Both different type boards placed on chambers
V.Peshekhonov
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CBM STRAW TRT
NECESSARY CONDITIONS FOR STABILITY OF
DETECTOR PARAMETERS
Mechanical For 4mm straws The change of the
signal amplitude by 10 from
-350µm sagitta

-200µm straw
elipticity
Drift velocity
A change by 6.24 per 1K and by 0.6 per 1mbar of
P
Gas mixture
A change of the Xe concentration or density by 5
upwards or downwards lead to a change of
the rejection power (by factor 1.5)
of the
streamer rate
Variation at the level of 1 for each gas
component is acceptable
Total straw gas volume is 30.56 m3 (4.45 m3 1M,
9.9 m3 2M, 16.2 m3 3M) Min gas flux
(similar required at LHC) is 0.058 m3 /min
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CBM STRAW TRT
TRT Services High-Voltage Power Supplies and
Distribution System Front-End Electronics Power
Supplies and Distribution System Gas System Gas
Cooling and Gas Ventilation (to provide the
temperature stability and to protect the straws
from humidity) Slow Control System
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03.10.2004