Download Characteristic Impedance Measurement

Characteristic Impedance Measurement of Pickup
Panel made up with a Suitable Dielectric Material,
and Surface Resistivity (Automation) for large
RPC electrodes
Manoj Kumar Singh
Department of Physics
Banaras Hindu University
Varanasi-221005.
Contents
Introduction to RPC Detector
Charge pick-up strip panel
Measurement of Characteristic Impedance
of pick-up panel
Surface Resistivity & its measurement
Future outlook
Summary
Acknowledgement
1
Resistive Plate Chamber (RPC) Detector
 Introduced in 1981 by R. Santonico and R. Cardarelli.
 Rugged and low-cost gas detector and extensively
used for the detection of charged particles.
 Time resolution < 2ns & position resolution few tens of µm.
2 mm
Graphite thick
coating on spacer
the outer
surfaces of
glass
 Electrodes (Glass / Bakelite) surface are coated with conductive paint .
 Gas mixture typically of Argon, Freon (R134a) and Isobutane.
 Localized charge produced due to the passage of ionizing radiation
through the gas volume, induces charge on appropriate read out strips.
2
Two Important part of RPC
 Pick-up strip panel
 Surface resistivity of electrodes
3
Pick-up Strip Panel
Requirements on dielectric material to be used for making the
Pick-up strip panel for the underground laboratories such as
INO (India Based Neutrino Observatory)
 Fire proof
 Water proof
 Flexible
 Light weight
 Cost effective
[Polycarbonate]
[Ceramic Foam]
 Characteristic Impedance match with external circuitry
 Locally Available
4
Making of Pick-up strip panel
We have studied several dielectric materials of which
we found ONLY TWO are close to our requirements
Ceramic Fiber
 Hard to keep strips and back sheet stick
Ceramic Foam
 Fireproof
 Flexible
 Light weight
 Moisture proof
 Thickness 2-3mm
7
Characteristic Impedance
 The characteristic impedance of a uniform transmission line is the ratio of the
amplitudes of a single pair of voltage and current waves propagating along the line in
the absence of reflections .
 It depend on the geometry and materials of the transmission line and for a
uniform transmission line it is independent of its length.
 It is purely a function of the capacitance and inductance distributed along the
line's length, and would exist even if the dielectric were perfect (infinite parallel
resistance) and the wires superconducting (zero series resistance).
5
Signal Reflection
 A signal in a cable is the sum of original signal and reflected signal traveling in the opposite direction.
 If the reflection of the signal lap with the original, it will cause distortion of the signal.
 Reflections occur when signals travel through two cables of different impedances, and occur at the
boundary interface of the two cables.
Pulse – Large reflection
(incorrect termination impedance)
Pulse – Virtually no reflection (close
matching of termination impedance)
 Signal reflection and distortion can be avoided between cables by matching their impedances to each other.
The NIM1 standard requires that all input and output device impedances and cables impedances be 50 ohms.
 But there are times when two cables or devices of two different impedances need to be interconnected to each
other. When this need arises, the principle of termination is used.
 Termination can be done either in series or in parallel or a combination of both.
6
Characteristic Impedance Measurement
Below circuit is used To
measure the CI of Pick-up strip
8
Characteristic Impedance Measurement
At 48.5Ω
for honeycomb
Waveform
of anbased
open pick-up
circuit panel
At
ofthickness
thickness4.0cm
5.0cm
At 48.5Ω
48.5Ω for
for Ceramic
Ceramic Foam
foam of
To remove the reflection completely we have to vary the thickness of
9
Dielectric material.
Automated Surface Resistivity Measurement
 The electrical resistance that exists between two parallel
electrodes in contact through the surface.
 The Ratio of DC voltage drop per unit length of the electrode to
current per unit width.
 The quality of coating will affects the distribution of HV very
seriously.
 Automated Scheme is important for the large number of
measurements.
 We require a suitable automated device to measure its surface
resistivity with good accuracy and in less time.
Methods to Measure the Surface resistivity
Method 1
 44 jigs of size ( 30 cm X 30 cm) attached by a plastic sheet.
 Individual ohmmeters will be used for each jig.
 Readings of all jigs collected simultaneously.
Time taken to record all the measurements would be about 3.47 days.
Finally Conducting Foam
will replace Cu-bars
11
Methods to Measure the Surface resistivity
Method 2
 Use two motors, of them one
motor will be for the motion
along Y-axis and another one
will be used along z-axis.
 Less number of ohmmeters will
be required ~ 6.
 Fully automated method by
using
data
interfacing
technique.
 Calculated
time
for
the
resistivity measurement with
six jigs (30cm x 30cm) and 60
RPM motor (5 mm shaft
diameter) ~3 days.
12
Methods to Measure the Surface resistivity
Method 3
 Use two motors for the X and Y axis
movement on aluminum bars. Third
motor for up and down movement of
Jig.
 Only one conductive foam jig and an
ohmmeter requires.
 Movement could be controlled
through PC using motor controller
kit.
 This would be fully automated
method by using data acquisition
system.
 Total time taken will be ~20 days
 Calibration of RPC can also be
done
13
Prototype 50 cm x 50 cm Fabrication
We focused on third method for the prototyping.
Aluminum bars
Belts
Wheel
Connecting wires
One DC (12V/DC/10RPM) motor and two DC
(12V/DC/60RPM)
Switches
Motor Bee Controller Kit
A conductive foam jig of (6x5 cm) size
14
Data Flow and Motor Control
DAQ
Motor
Bee
Controller
USB
Adopter
PC
USB
Adopter
15
Data View
16
Future works
Our next aim is:
To operate the movement of jig using motor controller kit with PC
 Two motors (12 V/DC/60RPM) are attached with one motor bee for
movement along x and y axis of the jig.
 One motor (12V/DC/10RPM) is attached with second motor bee in
same manner for up and down movement of the jig.
Circuit Diagram
17
Summary
 Ceramic foam seems to be good dielectric material for
the use in making pick-up strip panel.
 To measure the quality of coating & value of surface
resistivity of electrodes, and calibration of RPC detector
at large scale, we can use the suggested method to
control the motion of jig along three coordinates with
three motors.
 This measurement can be precisely completed in a short
period of time.
18
Acknowledgement
Deeply thankful to Shri Ravindra Raghunath Shinde,
Prof. B. Satyanarayana, my friends Abhishek
Kumar, Shivangi Shree and N. MariMuthu for helping
me.
 I am also grateful to the DST, New Delhi for
providing financial support and INO Collaboration
for providing me a challenging atmosphere to do
good work for our country.
Thank You!