Session SN: Instrumentation: Calibration and Electronics II

Experimental Approach to Finding an Energy Correction to the electron scattered into the Forward Tagger

The CLAS12 detector covers a large percentage of the $4\pi$ solid angle which allows detection of multi-particle final states. One of its new subsystems, the Forward Tagger (FT), provides an azimuthal angular coverage between $2.5^{\circ} < \theta < 4.5^{\circ}$. The detection of forward-angle scattered electrons at such small angles enables electroproduction experiments at low $Q^2$ providing an energy-tagged, polarized, high-intensity, quasi-real photon beam. Experiments relying on the FT need a very well calibrated subsystem to provide accurate information of the $e^\prime$ in order to complete physics analysis. One way to verify the FT energy calibration is using the missing mass technique, applying energy and momentum conservation, for well established reactions. For this study, the reaction $e p \rightarrow e^\prime p^\prime \pi^+ \pi^- $ was used in two ways by first allowing the $e^\prime$ to be missing and then the $p^\prime$. The results of both methods are compared and then applied to the data enabling a direct comparison before and after the $e^\prime$ energy correction.   

Machine learning application to event reconstruction from single-ended PMT readout

Machine learning (ML) has quickly found applications in high energy physics due to its potential to efficiently deal with large amount of event data and complex physics reconstruction modeling. This work explores the potential of ML for PROSPECT, the Precision Reactor Oscillation and SPECTrum experiment. PROSPECT is designed to perform a model-independent search for eV-scale sterile neutrino oscillation and measure the electron anti-neutrino spectrum from the High Flux Isotope Reactor (HFIR) located at Oak Ridge National Laboratory with high precision. The detector is filled with $\sim$ 4 ton $^6$Li-loaded liquid scintillator and highly segmented with double PMT readout on both ends of each segment. Neutrino events via the Inverse Beta Decay(IBD) interaction are reconstructed based on information including relative timing and individual light collection from both PMTs. In this talk, I will discuss the possibility of using machine learning techniques to reconstruct IBD events in segments with single functional PMT and improve cosmogenic background rejection capability in PROSPECT.   

Understanding electrical breakdown in liquid helium with a statistical distribution-based study

The neutron electric dipole moment (nEDM) experiment currently being developed to be mounted at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory will perform measurements in superfluid helium at a field of 75 kV/cm. Vital to achieving this high field is a better understanding of the electrical breakdown phenomenon, which limits the applicable potential and field. To that end, we have collected data on the distribution of the breakdown voltages for small electrodes immersed in liquid helium under varying conditions. We will show how the electrode area scaling of the breakdown field is determined from a statistical analysis of the data. The predicted scaling agrees well with the results obtained by our group for larger sized electrodes as well as those obtained by other investigators, and, importantly, can be extended to other noble liquids. We will show that the dependence of the probability of breakdown on field strength, extracted from the data, closely resembles that of field emission, giving a strong indication that the initial process involves field emission from the cathode. Lastly, a discussion of the many parameters affecting the breakdown including temperature, pressure, electrode surface polish, and electrode gap separation will be presented.   

Kmax-based data acquisition system for HI$\gamma$S

In 2018, the Compton program at HI$\gamma$S deployed two large-volume NaI detectors named DIANA and BUNI. Both detectors have multiple NaI segments and are read by several photomultiplier tubes. Because of the complexity of these detectors and their ability to provide very high count rates, a dedicated data acquisition(DAQ) system was needed. The newly developed DAQ system features CAEN V1730 waveform digitizers. The signals are recorded with 500MHz sampling frequency, preserving the pulse shapes for offline analysis. The recorded data are accessed through the VME bus by a Struck SIS3153 VME controller and transferred to the computer through a USB 3.0 connection. The combination of VME64X and USB 3.0 interfaces provide effective data transfer rates as high as 150 MB/s. A Kmax based software was developed to oversee the whole DAQ process with a user-friendly graphical user interface. The DAQ software also includes state of the art features like real-time histograms and pulse plotting. We will discuss the development and current status of the new Kmax-based DAQ system.   

High-Performance Counting-Mode DAQ for the Hall A Compton Polarimeter at Jefferson Lab

The Hall A Compton polarimeter can continuously measure the longitudinally polarized electron beam to high precision meeting the strict requirements of the JLab parity-violation program. There are two data acquisition systems employed: an integrating-mode DAQ for the photon detector and a counting-mode DAQ for the silicon microstrip tracking electron detector. Recently the counting-mode DAQ has been revived and upgraded with two novel electronics boards developed by the JLab Fast Electronics Group. The VETROC is a VXS-based electron trigger readout card. It is a high-rate (4 Gbps) pipelining TDC with 20 ps timing resolution. The VTP is a switch card module with greater FPGA trigger logic capabilities than past CTP and GTP designs used at JLab. In this VXS crate the VTP participates as the global-trigger and was programed as a VETROC and trigger scaler. This novel high-performance DAQ, capable of handling a trigger rate up to 200 MHz with a trigger deadtime of $<$ 10\% achieved, was employed in the recent CREX experiment and is a precursor for the needs of the future JLab high-precision SoLID and MOLLER programs. I will report on the performance of this counting-mode DAQ and the electron detector. I will also show the preliminary results of the Compton electron asymmetry for CREX.   

SpinQuest/E1039 FPGA Trigger

The SpinQuest(E1039) experiment is designed to extract the u-bar and d-bar Sivers functions through azimuthal asymmetry measurements of Drell-Yan induced dimuon pairs from 120 GeV/c proton beam interaction with polarized nucleon targets. A large combinatorial muon background produced in the beam dump magnet requires a trigger which identify dimuon pairs produced from the target in a high rate environment. The trigger system consists of four stations of scintillator hodoscopes whose 96 channels are digitized and processed by field-programmable gate array (FPGA) based VMEbus modules. Hodoscope hit patterns are compared to predetermined sets, chosen from Monte Carlo simulations, in a tiered lookup table to generate trigger decisions. The design and current status of the FPGA trigger as well as ongoing and planned upgrades to the trigger logic study will be presented.   

Correcting for helicity correlated beam parameters in the parity-violating electron scattering experiment of PREX-2 at Jefferson Lab.

In high precision parity-violating experiments such as PREX-2 at Jefferson Lab, understanding and correcting for differences in helicity correlated beam parameters is essential in removing false asymmetries from the experimental parity-violating measurement. To accurately measure possible helicity correlated beam parameters such as beam position, energy, and angle, these parameters are deliberately modulated in a controlled way and the response is measured in a series of monitors located along the beam line of the accelerator. Invertibility of the response matrix depends on the accelerator configuration and is required to express false asymmetries in terms of the beam parameters. Different combinations of parameter modulations with respect to beam monitors are examined to make this correction. The elements of this modulation system, its controls, and analysis will be discussed.    

Calibrating the sensitivity of high-rate asymmetry measurements to beam motion

The Lead Radius Experiment (PREX) is making a precise measurement of the parity violating asymmetry in polarized elastic electron-nucleus scattering to extract the neutral weak form factor and therefore the neutron RMS radius of $^{208}$Pb. PREX was proposed to measure the $\sim$0.6 ppm asymmetry with an overall uncertainty of better than 20 ppb (3$\%$). The total scattering event rate at the detectors is $\sim$4 GHz and is characterized by event-by-event statistical fluctuation in the raw asymmetry of $\sim$90 ppm standard deviation over 33 ms integrating time. In such a high rate measurement, detected asymmetries can be overwhelmed by fluctuations induced by random as well as helicity-correlated beam motion. Calibrating sensitivity to beam motion provides linear coefficients to remove its effect in asymmetry to first order. In addition, the grand averaged correction for beam motion can potentially make a sizable contribution to the central value of the observed raw detector asymmetry. Therefore precise and accurate sensitivity calibration techniques are crucial to achieve a small systematic uncertainty. In this talk, methods for analyzing calibration data, the size of beam corrections and their uncertainties from the recently completed PREX-II physics run will be discussed.