HyCal Repairs, Testing, and Upgrades

This page will have information about the repairs, tests, and upgrades of HyCal that are necessary for the running of PRad II, the Hidden Sector Search experiment, and the π ₀ Transverse Form Factor experiment.

HyCal Cable Upgrades in Hall B

As a part of the HyCal upgrades, the cables that attach to the computing crates needed to be changed to LEMO connectors for use in the Flash Analog-to-Digital Converters (FADC) boards that will be used in the crates for the upcoming experiments. These cables need to be removed from their original boards and refitted with the proper end connectors. Following this, each of the cables needed to be tested and fixed if there were any issues. This was done by utilizing a modified 32-pin connector at the end that will lead to HyCal that completed the circuit between cables that were opposite one another and one that paired cables that were next to each other. These linked cable then had a voltage of 5V sent through them to see if there were any issues in carrying the signal. In the case of lone cables or where a pair failed a terminator would be used on one cable and the same 5V signal would be sent to confirm which cables did not work. There were a total of 60 bundles of 32, 27, and 25 cables to test. The current status of this work can be views on the following spreadsheet PDF (Cable Testing Check Sheet). Two cables were found to not function properly and needed to be re-soldered to their boards that will connect to HyCal and 3 of those boards needed their 32-pin connectors replaced due to them cracking or being otherwise unusable.

After testing each of the cables, the cables were then re-bundled into groups of 16. The labeling was done to preserve the previous numbering scheme and adding an extra identifier after a period. For example the sub-bundles of 16 made from board 10.3 would be labeled 10.3.1 and 10.3.2 respectively. Bundle X.Y.1 would always have cables 1-16 and bundle X.Y.2 would always have the rest (depending on whether the original bundle had 32, 27 or 25 cables to begin with). These will then be used to map to the DAQ system for the new experiments with the new boards.

Meeting Update Slides for this Project

• Cabling Status Updated Slides for June 6, 2024
• Cabling Status Updated Slides for July 19, 2024

Contributors

• Aruni Nadeeshani (Mississippi State University)
• Buddhiman Tamang (Mississippi State University)
• Erik Wrightson (Mississippi State University)
• Mark Taylor (JLab Fast Electronics Group)

Special Thanks

• Thanks also goes out to the Hall B staff that helped with moving the floor grates to give better access to the cables.

This work was done in the Summer of 2024. THIS WORK IS ONGOING.

HyCal Optical Fiber and Connection Repairs

The optical fibers, plexiglass connectors, and light blocking coverings necessary for the Light Monitoring System (LMS) to send control signals to the HyCal modules required repairs to have all ~2000 modules in proper working order. These fibers can be used to test the various modules as well as be used as a control signal during experimentation and calibration. HyCal was brought to the ESB at JLab where an ePAS approval needed to be filed for the work as it involved clear UV-activated glue for securing the optical components to each module.

Initially, a map was made for the outer lead glass (PbGlass) and central lead-tungstate (PbWO₄) where the various repairs that needed to be done could be noted. Those working on creating this map were also asked to create a duplicate that just included information for the location of temperature sensors to that could then be used for updating the digital mapping in the DAQ for the new experiments and upgraded wiring system seen in HyCal Cable Upgrades in Hall B. This temperature sensor map can be seen in the two following spreadsheets ( PbGlass Temperature Sensor Map and PbWO₄ Temperature Sensor Map). Each of these two maps have one mapping showing using a (Row.Column) notation and one using the digital notation from the PRad Geant4 simulator. This form of double mapping was also kept for the optical repairs spreadsheet.

Once the maps were created and it was clear which modules needed to be repaired, the materials and ePAS approval were obtained the repairing and replacing the optical connections could begin on September 5, 2024. The current status of these repairs can be seen in the following PDF version of the repair mapping spreadsheets ( PbGlass Optical Fiber Repair Map and PbWO₄ Optical Fiber Repair Map). Please see this PDF for more detailed procedures of this process.

Repair of Crystals Beneath the Tungsten Absorber

The central 12 PbWO₄ crystals of HyCal surround a fitting for the beam to pass through the calorimeter. These crystals allow for an extremely tight angular coverage that makes HyCal so useful in experiments that require high precision at low angles like the PRad experiments. Mounted in this beam pipe fitting and covering the 12 crystals is a tungsten absorber. The optical fibers for the covered crystals must fed through holes on the absorber and then have a plexiglass optical donut connector affixed to the fiber and then attached to the crystals with UV activated glue. An extra challenge in this process is that the absorber when slid into its final position only has a very small gap from the crystals with the optical donuts needing to fit into pre-drilled holes within the absorber, but these holes are slightly smaller than the openings to the crystals. This necessitates a more precise placement of the connectors. Initially this difference was not quantified, so those working on the detector in person at the time (Aruni, Buddhiman, and Erik) consulted with Ashot Gasparian about the best way to go about figuring this out. With Ashot's advice, an impression was taken of one of the holes and then used to compare to the crystal openings and it was ensured that the alignment centered the holes above the crystal openings. As long as the optical donuts were placed in the center of each crystal with a tolerance of a few millimeters then the absorber would be able to be successfully seated. This was successfully done on September 26th, 2024.

Contributors

• Aruni Nadeeshani (Mississippi State University)
• Buddhiman Tamang (Mississippi State University)
• Erik Wrightson (Mississippi State University)
• Yuan Li (Shangdong University) [Damage Mapping Portion of this Project]
• Eugene Pasyuk (Jefferson Lab)
• Ashot Gasparian (North Carolina A&T State University)

Special Thanks

• Thanks goes out to the Hall B staff that helped with setting up the ESB space.
• Thanks goes out to Alexander Somov from Hall D for providing training and the materials for using the UV-activated glue.
• Thanks also goes out to Morgan Cook from the Hall B staff for helping us with setting up the ePAS for this work.

This work began in late August 2024 and had the last large repair work completed on September 27, 2024.

HyCal PMT Electrical Testing

The back side of HyCal opens up to allow access to the photo-multiplier tubes (PMTs) that attach to each HyCal module and capture the signal of the energy deposited in each one. The dynode signals of the PbGlass modules are passed out of the bottom of HyCal where they can be connected to fastBUS crates for data processing. These fastBUS crates do not need to be used for the upcoming experiments, but may be used if the crates are still in working order from the original PRad experiment. Each column of PMTs are connected to PC boards that then feed their anode signals out of the 32-pin connectors on the top of HyCal. Each PMT needs to be tested to ensure that it can properly respond to signals. These signals can be obtained from naturally occurring cosmic data from the atmosphere or stimulated signals via the LMS. For testing each PMT we unseat the PMT base from the PC board and then attach it to a breaker box adapter. This adapter grounds the base, inputs the needed high voltage bias, and carries the anode signal to an oscilloscope. Then once a signal can be confirmed attach the signal to the ADC and record and label the signal. The PMT base then can be re-seated in its previous position in the PC board. This should be done for each module to ensure they are in proper working order prior to testing the whole calorimeter at once. Please see this PDF for more detailed procedures of this process.

This work was done under the concurrent ePAS that also had the approval for the HyCal Optical Fiber and Connection Repairs Project while HyCal was present in the ESB. A high voltage interlock was in place so any high voltage signal would be cut off if HyCal's back door was opened. This work began on October 21, 2024 with the testing of a handful of modules with the main bulk work starting on October 22nd. The fan system was removed from HyCal by Hall B technicians. Please see this PDF (for PbWO₄ progress only) and this PDF (for PbGlass progress only) to see the progress of the checked modules so far. There is module specific notes to be found in an excel spreadsheet found in the PRad Logbook along with day to day updates of the work. Currently testing is only being done with cosmic data as the LMS in the process of being set up.

Meeting Update Slides for this Project

• PMT Electrical Test Status Update Slides for October 25, 2024
• PMT HV Electrical Testing Status for PRad Collaboration Meeting November 11, 2024 (by Erik Wrightson)

Contributors

• Aruni Nadeeshani (Mississippi State University)
• Buddhiman Tamang (Mississippi State University)
• Erik Wrightson (Mississippi State University)
• Jingyi Zhou (Duke University)
• Chao Peng (Argonne National Lab)
• Eugene Pasyuk (Jefferson Lab)
• Ashot Gasparian (North Carolina A&T State University)

Special Thanks

• Thanks goes to Youri Sharabian for designing the adapter box.

This work began in October 2024. THIS WORK IS ONGOING.

HyCal High Voltage Cable Testing in Hall B

Similarly to the HyCal Cable Upgrades in Hall B Project, the high voltage cables that will attach to HyCal each need to be tested prior to moving the calorimeter into the hall. HyCal requires high voltage to be supplied to each of its PMTs that are attached to each module.

Contributors

• Aruni Nadeeshani (Mississippi State University)
• Buddhiman Tamang (Mississippi State University)
• Erik Wrightson (Mississippi State University)
• Mark Taylor (JLab Fast Electronics Group)