H Proposal Defense - Revision history

Abdehait: /* Topic */

2012-12-15T23:01:54Z

Topic

Abdehait: /* The Signal Size */

2011-07-27T03:01:56Z

The Signal Size

Abdehait: /* The Thick Gas Electron Multiplier (THGEM) */

2011-07-05T17:22:32Z

The Thick Gas Electron Multiplier (THGEM)

Abdehait: /* Gas Electron Multiplication */

2011-07-05T17:06:28Z

Gas Electron Multiplication

Abdehait: /* Gas Electron Multiplication */

2011-07-05T16:55:58Z

Gas Electron Multiplication

Abdehait: /* Gas Electron Multiplication */

2011-07-05T16:54:44Z

Gas Electron Multiplication

Abdehait: /* Introduction */

2011-06-29T16:00:02Z

Introduction

Abdehait: /* References */

2011-05-17T01:31:18Z

References

Abdehait: /* The Thick Gas Electron Multiplier (THGEM) */

2011-05-16T23:09:01Z

The Thick Gas Electron Multiplier (THGEM)

Abdehait: /* The Thick Gas Electron Multiplier (THGEM) */

2011-05-16T23:07:25Z

The Thick Gas Electron Multiplier (THGEM)

@@ Line 6: / Line 6: @@
 =Topic=
-The Performance of Thick Gaseous Electron Multiplier Preamplifiers (THGEM) as a Neutron Sensitive Detector.
+The Performance of Thick Gaseous Electron Multiplier Preamplifiers (THGEM) as a Neutron Sensitive Detector. [[File: Proposal.pdf]]
 =Introduction=

@@ Line 182: / Line 182: @@
 An electron, freed by ionization and immersed in an external electric field, can ionize other atoms in a gas volume as a result of its acceleration in the external electric field.  The number of additional freed electrons can be determined  in terms of the external electric field (E), the pressure of the surrounding gas (P), and  two fit parameters (A & B) which depend on the gas properties  as shown in the equation <ref name="William"/>
-<math> \alpha= APe^{(\frac{-BP}{E})} </math>
+<math> \frac {\alpha}{P}= Ae^{(\frac{-BP}{E})} </math>
 The parameter <math>\alpha</math> is known as the Townsend coefficient.    In the case of a THGEM preamplifier,  an electric field (E) of <math>2 \times 10^4 \frac{\mbox{V}}{\mbox{cm}}</math> is established when a potential difference of 2 kV is applied between the top and bottom sides of the plate that are 0.1 cm apart.  In this work, the gas chamber contains a 1 Atm mixture that is 90% Argon and 10 % C02 by volume.  The parameters from reference <ref name="Sharma"> A.Sharma,F. Sauli, first tawsend coefficients measurements for argon gas european organization for nuclear research  (1993)  </ref > are not given for this mixture.  To estimate the THGEM pre-amplification, the A and B parameters for a 96/4 percent mixture gas mixture were used which are  5.04 <math>\frac{1}{\mbox{cm Torr}}</math> and 90.82 <math>\frac{\mbox{V}}{\mbox{cm Torr}}</math> respectively .

@@ Line 54: / Line 54: @@
 ===The Thick Gas Electron Multiplier (THGEM)===
-A Thick Gas Electron Multiplier (THGEM) is basically a GEM foil which has been scaled from microns to millimeter.  A THGEM card is made from FR4/G10 clad on both sides with copper. The THGEM cards for this work are 12x12 cm square plate that is 1 mm thick and coated with 17 um thick copper cladding.<ref name="Agocs"/> Each card is chemically etched to leave a copper trace around the perimeter as a border for a square area of a side length of 10 cm as shown in Fig. 7.  A thin layer (5 microns) of resistive paste (ED-7100) is applied to the card to allow a potential difference between the top and bottom layers and provide some spark protection by limiting the current flow along the surface. The card is machined to have 0.5 mm diameter holes. The resistive paste near the hole is machined away to form a 0.2 mm diameter rim around the hole. The holes are formed in a staggered array with a pitch of 0.8 mm.
+A Thick Gas Electron Multiplier (THGEM) is basically a GEM foil which has been scaled from micrometer to millimeter. A THGEM card is made from FR4/G10 clad on both sides with copper. The THGEM cards for this work are 12X12 cm square plates that are 1 mm thick and coated with 17 um thick copper cladding.2 Each card is chemically etched to leave a copper frame that surrounds an area of 100 cm2 as shown in Figure 4.A thin layer (around 5 micron) of ED-7100 resistive paste is applied (Figure 5) to allow potential �difference between the top and bottom layers and provide some spark protection by limiting the current flow along the surface. The card is machined to have 0.5mm diameter holes. The resistive paste near the holes is machined away to form a 0.2 mm thick rim around the hole. The holes are formed in a staggered array with a pitch of 0.8 mm.
@@ Line 62: / Line 74: @@
 |}
-The THGEM cards are fixed in place so the holes of each THGEM card is aligned by the  holders and separators in each corner.  The cards are separated from each other by a vertical distance of approximately  2.6 mm. A drift voltage card, cathode,  made of copper is placed at the top of the cards at a distance of 2.6 - 4 mm from the closest THGEM card.  The THGEM cards are all placed inside a chamber made of two pieces of machined ertalyte (plastic), with a kapton window on the upper piece as shown in Fig.8.
 [[File: THGEM_front.jpg | 250px|thumb| Fig.7 THGEM's chamber]]
-The gas chamber is constructed using two 29.5 X 29.5 X 1.25 cm sheets of ertalyte plastic and are bolted together by a number of M3 plastic screws located around the detector window to form a closed cavity around the THGEM cards. The ionization gas is a  90/10 percent Ar/CO2 gas flowing through the cavity with a pressure of 1 atm.
+A read out plane exists on the bottom the detector. It consists of �different width cop-
   [[File: read_out_plate_design.png | 250px|thumb| Fig.8 Read out plate design. ]]
-THGEM preamplipfier is robust with a higher operating voltage and relatively higher gain with the least discharge. It has 0.15 mm rim, 1 mm thick insulator and 2.6mm vertically separating distance from the next THGEM card, so the probability of discharge is minimized either in the card itself or with the other THGEM cards.  But the detector may have a higher noise compared to that of the GEM preamplifier.
+THGEM preamplipfier is robust with a higher operating voltage and relatively higher gain with the least discharge. It has 0.2mm rim, 1 mm thick insulator and 2.6mm vertically separating distance from the next THGEM card, so the probability of discharge is minimized either in the card itself or with the other THGEM cards.  But the detector may have a higher noise compared to that of the GEM preamplifier.
 =Detector Signal=

@@ Line 39: / Line 39: @@
 ===The Gas Electron Multiplier (GEM)===
-The Gas Electron Multiplier (GEM), invented by Fabio Sauli<ref name="Sauli1997"/> in 1997, is a modern method using electric fields to create an avalanche condition. A GEM is a 50 micron thick kapton foil clad on both sides with 5 microns of copper.  A staggered pattern of 50 microns diameter holes, equally spaced by distances comparable to the hole diameter, is etched into the copper clad foil.  The small size facilitates the use of low voltages (300 Volts)  to generate an electric field for amplification.  By comparison, the typical drift chamber, operating on the same principle, would need more than 1 kV to establish a similar electric field.
 {| border="1" cellpadding="4"

@@ Line 24: / Line 24: @@
 An electron from a primary ionization event needs to liberate more charge in order
-to create a detectable signal. One method to accomplish this amplti�cation uses strong
+to create a detectable signal. One method to accomplish this amplification uses strong
-electric �fields to accelerate the primary electron until it has sufficient energy to liberate
+electric fields to accelerate the primary electron until it has sufficient energy to liberate
-more electrons from the chamber gas. In a traditional drift chamber, an electric �field is
+more electrons from the chamber gas. In a traditional drift chamber, an electric field is
 established between two or more conducting wires. As an electron is accelerated towards a
 wire, it may obtain sufficient energy to ionize the chamber gas producing secondary freed
 electrons. The secondary electrons produced may themselves also be accelerated along the
-electric �field lines and cause further ionization in a process commonly referred to as an
+electric field lines and cause further ionization in a process commonly referred to as an
 avalanche.

@@ Line 23: / Line 23: @@
 =Gas Electron Multiplication=
-An electron from a primary ionization event needs to liberate more charge in order to create a detectable signal.  One method to accomplish this amplification uses strong electric fields to accelerate the primary electron until it has sufficient energy to liberate more electrons from the chamber gas.
+An electron from a primary ionization event needs to liberate more charge in order
-In a traditional drift chamber, an electric field is established between two or more conducting wires.  As an electron is accelerated towards a wire, it may obtain sufficient energy to ionize the chamber gas producing secondary freed electrons.  The secondary electrons produced may themselves also be accelerated along the electric field lines and cause further ionization in a process commonly referred to as an avalanche.
+to create a detectable signal. One method to accomplish this amplti�cation uses strong
 [[Image: streamer.png | 250 px|thumb|Fig.A streamer (more than one avalanche) <ref name="Holtzhausen">JP Holtzhausen, Dr WL VoslooHigh "Voltage Engineering Practice and Theory" ISBN: 978 - 0 - 620 - 3767 - 7</ref>

@@ Line 10: / Line 10: @@
 =Introduction=
-I propose to construct and measure the performance of a fission chamber instrumented with preamplifiers known a Thick Gas Electron Multipliers (THGEM).  This fission chamber is a chamber filled with an inert gas enclosing a fissionable target material, like Uranium or Thorium.  A neutron of sufficient energy has the potential to interact with  fissionable material producing heavy ions known as fission fragments.  The fission fragments  within 5 microns of the target's surface may escape the target as ions and ionize the gas in the chamber.  Electrons freed from the ionization gas can enter the THGEM preamplifier producing secondary electrons and directed to charge collectors using strong electric fields.
+I propose to construct and measure the performance of a fission chamber instrumented with preamplifiers known as a Thick Gas Electron Multiplier (THGEM). This fission chamber is a chamber filled with an inert gas enclosing a fissionable target material, like Uranium or Thorium. A neutron of sufficient energy has the potential to interact with fissionable material producing heavy ions known as fission fragments. The fission fragments within 5 micron of the target's surface may escape the target as ions and ionize the gas in the chamber. Electrons freed from the ionization gas can enter the THGEM preamplifier producing secondary electrons which are directed to collectors using strong electric fields.
-A THGEM preamplifier is a perforated fiberglass board (PC board) clad with a conducting material.  The design is based upon the Gas Electron Multiplier (GEM)  invented by Fabio Sauli in 1997<ref name="Sauli1997">F. Sauli, et al, NIM A386, (1997) 531-534 </ref >.   The GEM preamplifier is a 50 micron sheet of kapton that is coated on each side with 5 microns of copper.  The copper clad kapton is perforated with 50-100 micron diameter holes separated by 100-200 microns in a staggered array .  The THGEM preamplifier is more macroscopic version of the GEM foil that uses a 2 mm thick fiberglass sheet perforated with holes that are 2 mm in diameter.
+A THGEM preamplifier is a perforated fiberglass board (PC board) clad with a conducting material. The design is based upon the Gas Electron Multiplier (GEM) invented by Fabio Sauli in 1997<ref name="Sauli1997">F. Sauli, et al, NIM A386, (1997) 531-534 </ref >. The GEM preamplifier is a 50 micron sheet of kapton that is coated on each side with 5 micron of copper. The copper clad kapton is perforated with 50-100 micron diameter holes separated by 100-200 micron in a staggered array . The THGEM preamplifier is a more macroscopic version of GEM that uses a 2 mm thick fiberglass sheet perforated with holes that are 2 mm in diameter.
-The objective of this work will be to construct a THGEM based ionization chamber.  The THGEM will follow a proven design <ref name="Agocs">G. Agocs, B. Clark, P. Martinego, R. Oliveira, V. Peskov,gand P. Picchi,JINST, 3, P020112, 2008 </ref > and use a resistive paste to reduce discharge events.  The detector may be made sensitive to neutrons by doping the resistive paste with a fissionable material.  The doping step will take place once a working THGEM equipped detector has been demonstrated.  This fission chamber-like device will have the advantage of measuring the location of the incident neutrons that induced a fission event within the chamber by measuring the ionization signal using a segmented charge collector.
+The objective of this work will be to construct a THGEM based ionization chamber. The THGEM will follow a proven design <ref name="Agocs">G. Agocs, B. Clark, P. Martinego, R. Oliveira, V. Peskov,gand P. Picchi,JINST, 3, P020112, 2008 </ref > and use a resistive paste to reduce discharge events. The detector may be made sensitive to neutrons by doping the resistive paste with a fissionable material. The doping step will take place once a working THGEM equipped detector has been demonstrated.  This fission chamber-like device will have the advantage of measuring the location of the incident neutrons that induced a fission event within the chamber by measuring the ionization signal using a segmented charge collector.
 =Gas Electron Multiplication=

@@ Line 270: / Line 270: @@
 =References=
-  Web pages are not acceptable references.  A Thesis is acceptable.
 <references/>
 Paul Reuss ,Neutron physics,L'editeur EDP Sciences,2008.

← Older revision		Revision as of 23:09, 16 May 2011
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	The gas chamber is constructed using two 29.5 X 29.5 X 1.25 cm sheets of ertalyte plastic and are bolted together by a number of M3 plastic screws located around the detector window to form a closed cavity around the THGEM cards. The ionization gas is a 90/10 percent Ar/CO2 gas flowing through the cavity with a pressure of 1 atm.		The gas chamber is constructed using two 29.5 X 29.5 X 1.25 cm sheets of ertalyte plastic and are bolted together by a number of M3 plastic screws located around the detector window to form a closed cavity around the THGEM cards. The ionization gas is a 90/10 percent Ar/CO2 gas flowing through the cavity with a pressure of 1 atm.

−	A read out plane exists on the bottom of the detector.It consists of different width copper strips that are organized to have the same pitch such that the upper strip width is 50 micron and lower strip is 150 micron, the two strips are separated by a 25 or 50 micron thick layer of kapton . Both of the strips are glued on a 100 micron FR4 plate to achieve reasonable flatness as shown in Fig.8.~~<ref name="GDD"> GDD, 2001, May 12 2011, http://gdd.web.cern.ch/GDD/gemreadout.htm </ref>~~ The read out plane is vertically separated by a distance of 0.5 mm from the closest THGEM card and it is connected to 16 connectors, each connector has 20 traces. The 16 connectors are sent to a 130 pin adapter allowing the use of a digitization card known as the VFAT card which sends a digital signal to a break board and then to the DAQ system.	+	A read out plane exists on the bottom of the detector.It consists of different width copper strips that are organized to have the same pitch such that the upper strip width is 50 micron and lower strip is 150 micron, the two strips are separated by a 25 or 50 micron thick layer of kapton . Both of the strips are glued on a 100 micron FR4 plate to achieve reasonable flatness as shown in Fig.8. The read out plane is vertically separated by a distance of 0.5 mm from the closest THGEM card and it is connected to 16 connectors, each connector has 20 traces. The 16 connectors are sent to a 130 pin adapter allowing the use of a digitization card known as the VFAT card which sends a digital signal to a break board and then to the DAQ system.

← Older revision		Revision as of 23:07, 16 May 2011
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−	[[File: read_out_plate_design.png \| 250px\|thumb\| Fig.8 Read out plate design. ~~<ref name="GDD"/>~~]]	+	[[File: read_out_plate_design.png \| 250px\|thumb\| Fig.8 Read out plate design. ]]

	THGEM preamplipfier is robust with a higher operating voltage and relatively higher gain with the least discharge. It has 0.15 mm rim, 1 mm thick insulator and 2.6mm vertically separating distance from the next THGEM card, so the probability of discharge is minimized either in the card itself or with the other THGEM cards. But the detector may have a higher noise compared to that of the GEM preamplifier.		THGEM preamplipfier is robust with a higher operating voltage and relatively higher gain with the least discharge. It has 0.15 mm rim, 1 mm thick insulator and 2.6mm vertically separating distance from the next THGEM card, so the probability of discharge is minimized either in the card itself or with the other THGEM cards. But the detector may have a higher noise compared to that of the GEM preamplifier.