Session RN: Instrumentation: Targets and Luminosity

The Liquid Hydrogen Target for MUSE

The Muon Scattering Experiment (MUSE) at the Paul Scherrer Institute was built to measure elastic scattering of muons and electrons from a liquid hydrogen target in order to explore the proton radius puzzle and two photon exchange effects. MUSE performs measurements with both positively and negatively charged leptons with high precision. To accomplish this goal, MUSE employs a vertically movable target with five different target positions relative to the mixed e, $\mu $, and $\pi $ beam. The main target is a cylindrical Kapton cell with copper end caps that holds 280 mL of liquid hydrogen. In this presentation, we discuss the technical design, implementation, and performance of the target system and its support infrastructure, presenting data to demonstrate the successful operation of the LH$_{\mathrm{2}}$ target.   

A Liquid Hydrogen Target for TPEX

Recent experiments at Jefferson Lab seem to indicate that two-photon exchange contributions must be included in elastic electron-proton scattering to correctly extract the proton elastic form factor. However, experiments performed to specifically study two-photon exchange (VEPP-3, CLAS and OLYMPUS) have so far shown little evidence for significant contributions beyond single photon exchange up to Q$^{\mathrm{2}}=$2.5 (GeV/c)$^{\mathrm{2}}$. TPEX, the Two-Photon Exchange eXperiment at DESY proposes to extend those measurements up to Q$^{\mathrm{2}}=$4.7 (GeV/c)$^{\mathrm{2}}$, where the contributions are expected to be significantly larger. In order to compensate for the lower cross sections at the higher energies required to reach those large momentum transfers, TPEX plans to build a new liquid hydrogen target that will yield a luminosity about a factor of 200 times higher than that of the OLYMPUS experiment. In this presentation, we will discuss the requirements and the technical design of the liquid hydrogen target for TPEX.   

High Luminosity Lead-208 Targets for the PREX-2 experiment

The Lead Radius Experiment (PREX-2) successfully ran in Jefferson Lab’s Hall A in the Summer of 2019. In order to achieve low angle and high rate for the high precision parity violating electron scattering measurement it is necessary to design and implement a target and collimation system which is capable of high luminosity, isotopically pure, thermally and structurally stable, and sufficiently radiation shielded. The experimental collaboration built upon the experience of the previous design of a lead-diamond sandwich enclosed in a copper jacket with active cooling. We will report on the improved design and implementation of these targets, and summarize their performance during the PREX-2 run.   

Development of SOLSTISE: A Supersonic Gas Jet Target for Solenoidal Spectrometers

The SOLenoid and Supersonic Target in Structure Experiments (SOLSTISE) is a gas jet target currently under development at Oak Ridge National Laboratory, designed for use inside the solenoidal spectrometer SOLARIS at the Facility for Rare Isotope Beams. Experiments utilizing solid targets often have increased backgrounds from unwanted reactions on contaminants and suffer from worsened energy resolution due to energy loss straggling in the target material. In addition, the kinematic compression introduced when measuring transfer reactions in inverse kinematics with traditional silicon detector setups amplifies these issues. SOLSTISE and SOLARIS offer a unique solution to both problems, making their combination the ideal setup for many potential measurements of reactions on exotic nuclei. Rapid part fabrication via additive manufacturing has allowed SOLSTISE to be designed to minimize particle shadowing from the gas piping infrastructure while reducing background pressures, and nitrogen jet densities up to 5x10$^{\mathrm{18}}$ atoms/cm$^{\mathrm{2}}$ have been demonstrated. Current designs and simulation data will be presented.   

Simulation and Performance of~Radiation Shielding for~Recent and Future~Parity-Violating Electron Scattering~Experiments~at~Jefferson Lab~

The parity-violating asymmetry resulting from~the~weak interaction,~when a longitudinally polarized electron beam is scattered from an unpolarized target,~can be used to probe nuclear structure~or to~test the limits of~the~Standard Model. The~PREX-2~and~CREX~experiments used~1 GeV and 2.2~GeV~electron~beams respectively,~elastically scattering from the Pb-208 and Ca-48 nuclei to~measure the neutron skins that constrain the nuclear symmetry energy and~models of nuclear structure.~MOLLER is~a~future experiment~that will~scatter~an~11 GeV electron beam from atomic electrons in a liquid Hydrogen target~to measure the electroweak mixing~angle and~compare against Standard Model predictions as an indirect search for new physics.~Such a search is~currently beyond the energy scale reachable by direct searches.~An important aspect of the experimental design~is radiation shielding optimization to~suppress physics backgrounds~and~mitigate damage to the experimental~instruments~and hall infrastructure. This talk summarizes~the optimization studies~currently underway for MOLLER,~particularly discussing the effects~on collimators, magnets, detectors,~and experimental hall;~considering~the lessons learned from simulation and performance of radiation shielding for the PREX-2/CREX experiments.   

Radiation Shielding and Dose Estimation for Nuclear Physics Experiment.

Precise estimation of the radiation dose which can occurred during any nuclear physics experiment is very important, this helps us to design and develop the shielding for nuclear physics experiments accordingly and prevent any catastrophic damages to equipment. The simulation for radiation dose measurement was done using GEANT4 for PREX-II and MOLLER experiments. The dose measurement was done for neutron, and photon on detectors at different locations and compared to an experimental result. We found that, the result obtained from the simulation using GEANT4 is in close approximation to the actual dose during the PREX-II experiment providing a benchmark for simulation estimations of radiation dose. This result will be valuable for other upcoming MOLLER experiment in designing and developing realistic radiation shielding measures while minimizing the cost and effort.