NSF Final Report AwardNum0653570 - Revision history

Oborn: /* Readout switchyard */

2009-09-11T18:53:59Z

Readout switchyard

Oborn: /* Preamplifier design and procurement */

2009-09-08T15:53:02Z

Preamplifier design and procurement

Oborn: /* Readout switchyard */

2009-09-08T15:22:34Z

Readout switchyard

Oborn: /* Readout switchyard */

2009-09-08T15:22:17Z

Readout switchyard

Oborn: /* What are your major findings from the activities identified above */

2009-09-02T23:08:37Z

What are your major findings from the activities identified above

Oborn: /* Ionization Chamber Construction */

2009-09-01T23:59:19Z

Ionization Chamber Construction

Oborn: /* Ionization Chamber Construction */

2009-09-01T23:58:56Z

Ionization Chamber Construction

Oborn: /* Charge Collector Design */

2009-09-01T23:44:06Z

Charge Collector Design

Oborn: /* Charge Collector Design */

2009-09-01T23:43:49Z

Charge Collector Design

Oborn: /* Charge Collector Design */

2009-09-01T21:19:30Z

Charge Collector Design

@@ Line 69: / Line 69: @@
 [[Image:VFAT_Breakout_REV3_Design_Schematic.png | 400 px]]
 [[Image:VFAT_Breakout_REV3.png | 400 px]]
 === Physics Analysis===

@@ Line 29: / Line 29: @@
 Figure 2 below shows the custom designed GEM preamplifier for the Qweak Region 1 tracking system.  The preamplifier is a 50 micron thick kapton foil clad on both sides with 5 microns of copper.  Holes are etched into the foil such that a high voltage (HV) applied across the top and bottom copper plates will create an electric field strong enough to cause charge to pass through the hole and multiply much like the avalanche region of a drift chamber.    Engineers from the Idaho Accelerator Center (IAC) designed the shape of the foils and the location of 6 tabs used for HV connections, as shown in the left hand figure below.  This generic design allows one to use the part for any GEM amplification stage simply by cutting off the unused HV tabs.  The actual preamp is shown on the right hand side of the figure below.   Although this is a simple part, it is a clear example of how the infrastructure at the IAC can be leveraged in support of our physics mission.
-[[Image:Qweak_GEM_preamp.jpg | 300 px]][[Image:Qweak_GEM_preamp_TecEtch.jpg | 300 px]]
+[[Image:Qweak_GEM_preamp.jpg | 300 px]][[File:GEM_Foils_mounted_on_the_frame_1.jpg|250px]]
 :Figure 2: The GEM preamplifier design and a picture of the manufactured part.

@@ Line 67: / Line 67: @@
 [[Image:BreakOutBox.jpg | 400 px]]
 [[Image:VFAT_Breakout_REV3.png | 400 px]]
 === Physics Analysis===

@@ Line 67: / Line 67: @@
 [[Image:BreakOutBox.jpg | 400 px]]
+[[Image:VFAT_Breakout_REV3.png | 400 px]]
 === Physics Analysis===

@@ Line 76: / Line 76: @@
 ==What are your major findings from the activities identified above==
-During the past year there are three findings which should be reported.  The first finding was the proof in principle of a candidate readout system for the Qweak experiment.  The second finding is a comparison between an analysis currently underway by the graduate student on this grant with a previous experiment.  The third finding was a serendipitous result involving experimentation with a drift chamber system under study.
+In addition to completing the construction of the Region 1 tracking chambers for Qweak, the support from this proposal resulted in several findings.  The first finding was a proof in principle of a candidate readout system for the Qweak experiment.  A measurement of the pion center of mass phi angle distribution is the second finding to report.  The third finding was a serendipitous result involving experimentation with a drift chamber proto-type system for JLab’s Hall B.
 ===Qweak readout  Speed tests====
-The VFAT is a candidate front end readout card for Qweak's region 1 tracking system.  The VFAT chip has been designed to sample the detector analog output at 40 MHz.   Although elastically scattered electrons which traverse the entire Qweak apparatus are expected to trigger the readout system at rates of about 1 kHz, there is a large background due to moller scattering which corresponds to rates of 12 MHz/nA uniformly distributed over the entire region 1 acceptance.   The moller rate on a single detector strip would be about 25 kHz/nA.  This restricts the region 1 tracking system to operating currents below 400 nA since the detector rise time of 50 nanoseconds will result in signal pileup if the ionization particle flux rates exceed 10 MHz.  The VFAT board by itself can satisfy the readout requirements of Qweak.
+The VFAT is a candidate front end readout card for Qweak's region 1 tracking system.  The VFAT chip has been designed to sample the detector analog output at 40 MHz.   Although elastically scattered electrons which traverse the entire Qweak apparatus are expected to trigger the readout system at rates of about 1 kHz, there is a large background due to moller scattering resulting in electron rates of 12 MHz/nA uniformly distributed over the entire region 1 acceptance.   The moller rate on a single detector strip would be about 25 kHz/nA.  This restricts the region 1 tracking system to operating currents below 400 nA since the detector rise time of 50 nanoseconds will result in signal pileup if the ionization particle flux rates exceed 10 MHz.  The VFAT board sampling at 40 MHz would, by itself, satisfy the readout requirements of Qweak.
-The remaining question is whether the transfer of the VFAT digital output to the data acquisition system without introducing a bottleneck.  The CERN engineer who designed the VFAT board suggested the use of a Field Programmable Gate Array (FPGA).   THE VME 1495 FPGA I/O module from CAEN was selected for testing.  We observed read and write speeds between the VME backplane and the FPGA user registers of 16 bits to USER FPGA in 330 ns.  This measurement correspond to a throughput speed of  6 MB/sec compared to a requirement of 0.5 kb/sec for Qweak.
+The remaining question is whether the VFAT digital output can be transferred to the data acquisition system without introducing a bottleneck.  The CERN engineer who designed the VFAT board suggested the use of a Field Programmable Gate Array (FPGA).   Based on that recommendations, we decided to test a VME 1495 FPGA I/O module from CAEN.  We observed read and write speeds between the VME backplane and the FPGA user registers of 16 bits to USER FPGA in 330 ns.  This measurement corresponds to a throughput speed of 6 MB/sec compared to a requirement of 0.5 KB/sec for Qweak.
 ===Comparison with other experiments===
-In addition to working on Qweak hardware,  the graduate student on this grant is also analyzing data from a previous experiment for the physics part of her thesis.  The data was taken in JLAB’s Hall B as part of the polarized structure function program.  Tamar is interested of using that data set to extract the ratio of the polarized down quark distribution to the unpolarized (Δd/d).  Semi exclusive pion production will be used to extract this ratio.  As a first step, Tamar has looked at single pion production in the exclusive channel  H(e,e’π)n, where the neutron is detected using missing mass techniques.  Figure 1 below shows the observed counting rate as a function of the pion phi angle in the center of mass frame.  The data is compared with the unpolarized experiment E99-107 by ignoring the beam and target polarization information in the EG1 experiment.
+In addition to working on Qweak hardware, the graduate student on this grant, Tamar Didberidze, is also analyzing data from a previous experiment for the physics part of her thesis.  The data under analysis was taken in JLab’s Hall B as part of the polarized structure function program.  Tamar is interested in using that data set to extract the ratio of the polarized down quark distribution to the unpolarized (Δd/d).  Semi exclusive pion production will be used to extract this ratio.  As a first step, Tamar has looked at single pion production in the exclusive channel  H(e,e’π)n, where the neutron is detected using missing mass techniques.  Figure 1 below shows the observed counting rate as a function of the pion phi angle in the center of mass frame.  The data is compared with the unpolarized experiment E99-107, also done using the CLAS, by ignoring the beam and target polarization information in the EG1 experiment.
 Cuts: EC_inner>0.06, EC_tot/p>0.2, nphe>2.5, <math>0.9<M_x<1.1</math>, <math>1.1<W<1.5</math> and <math>0.6<cos\theta_{pion}^{CM}<0.8</math>.<br>
 [[Image:phi_angle_cm_frame_vs_rate_two_results_compared_cos_theta_0-6_0-8.jpg|500px]]<br>
 ===Drift Chamber Feedthroughs===
-As part of her graduate studies, Tamar Didberidze has been quantifying the performance of two proto-type drift chambers for Hall-B. The ionization chamber principle is similar to the GEM chambers being built for Qweak and was a good training experience for her until the Qweak chambers are completed.   Two ionization chamber proto-types were built by JLab and sent to ISU. They are identical except that one uses an all plastic feedthrough to hold the drift chamber wires and another has a plastic feedthrough with a metal tip where the wire makes contact with the feedthrough. The proto-type detectors will be used to evaluate the efficency of the chamber as a function of the ionizating particles position from the end of the wire. A Garfield simulation leads one to believe that the plastic tipped feedthrough will result in a less efficent detector near the end of the wire due to a less radial electric field lines. The answer to this question will impact the design of drift chambers for the CLAS 12 upgrade.  During this funding cycle, Tamar has discovered that the proto-type detector using plastic feedthroughs is noisier than the one which has metal tips.
+As part of her graduate studies, Tamar Didberidze has been quantifying the performance of two proto-type drift chambers for JLab’s Hall B. The ionization chamber principle is similar to the GEM chambers being built for Qweak and provided a good training experience for her before beginning constructing the Qweak chambers.   Two ionization chamber proto-types were built by JLab and sent to ISU. They are identical except that one uses an all plastic feedthrough to hold the drift chamber wires and another has a plastic feedthrough with a metal tip where the wire makes contact with the feedthrough. The proto-type detectors will be used to evaluate the efficiency of the chamber as a function of the ionizing particles position from the end of the wire. A Garfield simulation leads one to believe that the plastic tipped feedthrough will result in a less efficient detector near the end of the wire due to less radial electric field lines. The answer to this question will impact the design of drift chambers for the CLAS 12 upgrade.
 [[Image:discriminator_threshold_vs_rate_using_VPI_Post_Amp_for_Metalica_and_Plastika_HV_1450V_1500V_1.jpg|400px]]
 [[Image:HRRL_16-04-09_Position_vs_Rate_ADCMeasuremts_AllData_UsingSimpleErrorCalculation.jpg|400px]]
 ==What research and teaching skills and experience has the project helped provide to those who worked on the project==

@@ Line 46: / Line 46: @@
 [[Image:QweakR1_TopWindowOverlayedOntoElectronProfile_1.jpg | 400px]][[File:QweakR1_Detectors_Overlayed_E-profile.png | 450 px]]
-:Figure 4.  Left: A full scale picture of the electron profile and the top half of the ionization chamber. Right: Completed Region1 tracking system.  The which paper on top of the entrance window represents elastic electrons which enter Cherenkov detectors used to measure the parity violating asymmetry.
+:Figure 4.  Left: A full scale picture of the electron profile and the top half of the ionization chamber. Right: Completed Region1 tracking system.  The which paper on top of the entrance window represents elastic electrons which enter the Cherenkov detectors used to measure the parity violating asymmetry.
 === Qweak readout electronics ===

@@ Line 42: / Line 42: @@
 ==== Ionization Chamber Construction====
-The ionization chamber for the Qweak Region 1 tracking system needs to have a small profile in order to be placed less than a quarter meter after the target.  A collimator in front of this detector divides the electron scattering anglular range into octants which reduce the angular acceptance range by about 30 percent.   The goal was to construct a chamber which did not interfere with the other octants and be transportable between octants.  The figure below shows the top half of the ionization chamber which has been built.  As seen in the figure, the electron profile is enclosed by the detector acceptance and the ionization chamber frame is in the shadow of the collimator.  The HV distribution board has been designed by physics undergraduate student Jordan Keough and is ready to be sent out for production.  Chamber construction will be completed when the charge collector arrives from the vendor and is installed.  We expect to test the chamber in August, 2008.
+The ionization chamber for the Qweak Region 1 tracking system is placed less than a quarter meter after the target and has a small profile.  A collimator in front of this detector divides the electron scattering angular range into octants reducing the angular acceptance range by about 30 percent.   The goal was to construct a chamber which moves between octants and does not interfere with adjacent octants.  The left picture in Figure 4 shows the top half of the ionization chamber placed on top of a full scale representation of electrons exiting the first collimator in front of Region 1.  Both graduate students, Julian Salamanca and Tamar Didbaridze, contributed to the construction of the Qweak chambers.  As seen in Figure 4, the electron profile is enclosed by the detector acceptance and the ionization chamber frame is in the shadow of the collimator.  The completed chambers are shown on the right hand side of Figure 4. A HV distribution board was designed by physics undergraduate student Jordan Keough and is visible along with BNC connectors near the top of the detectors.
 [[Image:QweakR1_TopWindowOverlayedOntoElectronProfile_1.jpg | 400px]][[File:QweakR1_Detectors_Overlayed_E-profile.png | 450 px]]
 === Qweak readout electronics ===

@@ Line 34: / Line 34: @@
 ==== Charge Collector Design ====
-The charge collector for Qweak's region 1 tracking system is shown in Figure 3.  One layer of the copper charge contains a series of concentric strips aligned with the electron scattering angle <math>\theta</math>.  Each of the red strips shown on the left side in Figure 3 is 400 microns wide and will measure the elastic electron scattering angle to within 0.1 mrad.  The blue lines, shown in the middle figure, are representative of the <math>\phi</math> scattering angle.  A large number of graduate student hours were needed to place each strip into the correct position using PC board design software.  Software compatibility issues with the vendor were also a major time sink of several months before the part could be accurately manufactured according to our specifications.  This single part represents 6 months of graduate students and is one example of a practical component to a students educational experience.   The photo in Figure 3 shows the final charge collector delivered on 11/12/08.
+The charge collector for Qweak's region 1 tracking system is shown in Figure 3.  One layer of the copper charge contains a series of concentric strips aligned with the electron scattering angle <math>\theta</math>.  Each of the red strips shown on the left side in Figure 3 is 400 microns wide and will measure the elastic electron scattering angle to within 0.1 mrad.  The blue lines, shown in the middle figure, are representative of the <math>\phi</math> scattering angle.  A large number of graduate student hours were needed to place each strip into the correct position using PC board design software.  Software compatibility issues with the vendor were also a major time sink of several months before the part could be accurately manufactured according to our specifications.  This single part represents 6 months of graduate students and is one example of a practical component to a student's educational experience.   The photo in Figure 3 shows the final charge collector delivered on 11/12/08.
 [[Image:BOTTOM_copper.jpg | 350px]][[Image:TOP_copper.jpg | 350px]][[Image:CERN_Qweak_Charge_Collector_2.jpg | 350px]]