Conveners
Polarized Ion and Lepton Sources and Targets: Sources and Targets I
- Erdong Wang (BNL)
Polarized Ion and Lepton Sources and Targets: Sources and Targets II
- Marcy Stutzman (JLab)
Polarized Ion and Lepton Sources and Targets: Sources and Targets III
- Joe Grames (JLab)
Polarized Ion and Lepton Sources and Targets: Sources and Targets IV
- Todd Averett (W&M)
Polarized Ion and Lepton Sources and Targets: Sources and Targets V
- Chris Keith (JLab)
Polarized Ion and Lepton Sources and Targets: Sources and Targets VI
- James Maxwell (JLab)
Polarized Ion and Lepton Sources and Targets: Sources and Targets VI
- Matt Poelker (JLab)
Currently, GaAs-based photocathodes with CsO activation layer serve as the practical source of polarized electrons. However, a thin CsO layer is susceptible to vacuum poisoning. Recent studies have shown that graphene, when applied as a thin layer, can effectively hinder the reaction between reactive gas molecules like oxygen and carbon dioxide. However, the deposition of a monolayer 2D...
Researchers at University of California Santa Barbara and Jefferson Lab investigated growth of high polarization heterostructure GaAs photocathodes using either chemical- or molecular-beam epitaxy (CBE or MBE). High polarization photocathodes are required to generate electron beams for particle accelerator physics experiments, and there is an urgent need to to re-establish a source of high...
The talk will summarize the state of the art of photocathode based on III-V semiconductor for spin polarized electron beam production and illustrate the limitations that have prevented this class of materials to provide a long term reliability at the highest average beam currents necessary for some of the new accelerator facilities or proposed upgrades of existing ones.
This points to the...
The operating lifetime of GaAs-based photocathodes in DC high-voltage electron photo-guns is limited by ion back-bombardment, where ions created within the photo-gun potential are accelerated toward the photocathode. This leads to an undesired reduction of the photocathode quantum efficiency (QE). At the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab, experiments were...
The high-intensity, polarized electron source is a critical component for the electron-ion collider, requiring a polarized electron gun with higher voltage and higher bunch charge than any existing polarized electron source. At Brookhaven National Laboratory, we have built and successfully conditioned an inverted HVDC photoemission gun up to 350 kV. In this study, we report on the performance...
The use of polarized $^3$He ions in storage rings opens a new window to investigate nuclear forces, because the spin-dependent part of the differential cross section of the observed reactions must stem in first order from the neutron spin. Thus, nuclear polarized $^3$He$^{2+}$ beams can be regarded as an ideal substitute for polarized neutron beams. Polarized $^3$He ions were used in the...
Our study of atomic beams passing through a static magnetic field, whose direction reverses along the axis of motion, gave rise to a new, versatile polarization method. For instance, a sinusoidal magnetic field entails a radial component, which is proportional to the gradient in the longitudinal direction. Such a field can be generated by two opposing solenoid coils. As a particle beam travels...
The Optically Pumped Polarized Ion Source (OPPIS) provided polarized H$^-$ to the injector chain of the RHIC. The scheme used in the OPPIS is as follows: An atomic hydrogen beam produced by an external source is injected into a He-gas ionizer cell inside a high magnetic field solenoid to produce a proton beam. This proton beam then passes through an optically pumped Rb vapor cell and picks up...
A suite of experiments measuring target-spin observables in electron-nucleon scattering (dubbed Run Group C) was recently executed in Jefferson Lab. These experiments involved the scattering of an 11 GeV electron beam from longitudinally polarized nucleon targets located within the CLAS12 spectrometer in Hall B. The dynamically polarized target used in these experiments was designed and...
Polarized $^3$He nuclear targets have been invaluable surrogates for polarized neutron targets in spin-dependent scattering studies of the quark and gluon structure of matter. Traditional polarized $^3$He targets have seen dramatic improvements in the last three decades, however they have been limited in their use in spectrometers that utilize high-magnetic-field tracking systems, such as...
The physics program for Hall B at Jefferson Lab includes multiple, high-impact experiments scattering electrons from transversely polarized protons. These experiments will measure, for example, the Transverse Momentum Distributions and the Generalized Parton Distribution for protons, using, respectively, semi-inclusive deep inelastic scattering and deeply virtual Compton scattering. In this...
Dynamic nuclear polarization (DNP) is technique used to enhance the nuclear spin polarization of materials. DNP works by using microwaves to continuously drive spin transitions in a material that is doped with free radicals, and placed inside a 1 K environment in a high magnetic field. Once enhanced, the nuclear polarization can be determined by analyzing the lineshape of the NMR absorption...
The polarized target is an essential part of the experimental program at the Bonn accelerator facility ELSA. In recent years, the polarized target has been successfully used in various experiments to measure single and double polarization observables at the Crystal Barrel Detector at ELSA. Since our experimental program is limited to real photons, we use the classical frozen spin target...
The SpinQuest experiment at Fermilab aims to measure the Sivers asymmetry for the light sea quarks in the longitudinal momentum fraction range of 0.1 < $x_B$ < 0.5 from the Drell-Yan process. A nonzero Sivers asymmetry measurement would be indicative of a nonzero orbital angular momentum contribution from the sea quarks. The SpinQuest experiment uses the proton beam from Fermilab’s 120 GeV...
The SpinQuest polarized target system at Fermilab uses a continuous flow helium-4 evaporation refrigerator to provide the required cooling power during the dynamic nuclear polarization (DNP) process and the intense proton beam from the 120 GeV main injector. The refrigerator was designed in compliance with the American Society of Mechanical Engineers (ASME) to pass the cryogenic safety review...
We have developed a novel type of magnetic compass based on a spinning Hall probe. It is used for determination of the magnetic field direction in the polarized He-3 target during the GEn experiment. This compass does not require prior calibration and has no problem with probe signal drift. Obtained accuracy is better than one milli radian. The compass concept and design will be presented.
In 1984, when the Triangle Universities Nuclear Laboratory was building a polarized ion source there was an effort to build new cryogenic nuclear targets that could be used for measurements of neutron-nucleus spin interactions and later, searches for parity and time reversal violation in the neutron-nucleus interaction. The initial statically polarized targets were cooled to near 10 mK in a 7...
Recent experiments at Jefferson National Laboratory (JLab) utilize polarized $^3$He targets at high luminosity to study the structure functions and elastic form factors of the neutron. One experiment explores the spin asymmetry in the virtual photoabsorption cross section on the neutron, $A_1^n$. This experiment ran at JLab early to mid 2020. The other experiment explores the neutron electric...
Nucleon elastic form factors encode crucial information about its charge and magnetization distributions. For many decades, nucleon form factors were studied by using unpolarized electron-nucleon cross section measurements. The advent of electron beams with higher luminosities and beam polarization coupled with large acceptance detectors, polarized targets and recoil polarimeters enabled a...
Polarized fuels in a tokamak fusion reactor can increase the cross section by 50%, and the power gain of an ITER-scale fusion reactor by 75%. The question is: can polarized materials survive inside a hot fusion plasma for times long enough to reap these expected gains? An in−situ polarization survivability test in a tokamak plasma is planned to address this. In a recent proposal...
The COMPASS experiment at CERN used a transversely solid polarized deuteron target with a muon beam to measure the TMD PDFs in SIDIS in 2022.
The target system consists of a 50 mK dilution refrigerator, a 2.5 T solenoid magnet, and three sets of 70 GHz microwave systems. Solid $^6$LiD beads of the target material were contained in 3-target-cell of 30-60-30 cm long with 3 cm in diameter. The...
The process of Dynamic Nuclear Polarization (DNP) requires a magnetic field that is simultaneously very strong (2.5 - 5 T) and very uniform (dB/B ≤ 10-4). Often, this is achieved by supplementing an existing strong field already incorporated into a spectrometer with small correction coils internal to the target. This active polarization technique allows for continuous polarization...
