Session GI: Instrumentation III

Development of a Hybrid Multipolar RF trap for Precision Measurements

This contribution will present the development of a hybrid ion trap capable of operating in different trapping configurations. The trap is designed with the intention of capturing and performing precision studies of atoms and molecules containing short-lived isotopes produced at radioactive beam facilities. The physics goals include entangled-state isotope shift measurements for searches of King nonlinearity from BSM couplings, trapping molecular ion nuclear EDM searches, and obtaining higher-order nuclear structure observables. The various trapping configurations are simulated in COMSOL, where stability regions are mapped out and typical ion trajectories are characterized. Simulations and experimental progress will be presented.   

Time-Dependent Impact Ionization in a Large-Size Ge Detector Made from a Crystal Grown at USD

SuperCDMS-style Ge detector made from a crystal grown at USD was operated at the University of Minnesota to observe the time-dependent impact ionization. An Am-241 movable source was used to characterize the energy spectra. The observed time-dependent impact ionization at mK temperature can be explained due to the formation of cluster dipole states. We studied the charge transport properties inside the detector at a cryogenic temperature and attempted to understand the charge collection efficiency using an empirical model. The binding energy of the charged state, A^-, was accounted for in the order of < 1meV and impact ionization scattering cross-section in the order of 10^-13 cm².

    

Development of the St. Benedict Paul trap for tests of the Standard Model

Nuclear beta decays provide a unique avenue for testing the electroweak part of the Standard Model through precision measurements. Physics beyond the Standard Model would manifest itself in these transitions through a variety of possible effects including a non-unitarity of the Cabibbo-Kobayashi-Maskawa quark mixing matrix, scalar or tensor currents, and interactions involving right-handed neutrinos. Probing these various effects in superallowed mixed beta decay transitions can be done through precision measurements of the beta-neutrino angular correlation parameter. As such, we are currently constructing at the Notre Dame Nuclear Science Laboratory the Superallowed Transition Beta-Neutrino Decay Ion Coincidence Trap (St. Benedict). St. Benedict will take radioactive a ion beam produced by TwinSol, thermalize it in a large volume gas cell, then transport it into two separate differentially-pumped volumes using a radio-frequency (RF) carpet and a radio-frequency quadrupole (RFQ) ion guide before injecting it in an RFQ trap to create cool ion bunches for injection in the measurement Paul trap. The St. Benedict scientific program and the development of the Paul trap will be presented.

    

Beam particle identification and tagging of incompletely stripped heavy beams

One of the primary challenges in performing successful inverse-kinematics measurements with heavy nuclei is the successful identification and tagging of the beam, which often contains many species. For this purpose, the Heavy Isotope Tagger (HEIST) was developed and commissioned at the National Superconducting Cyclotron Laboratory (NSCL).  HEIST utilizes two micro-channel plate timing detectors to measure the time-of-flight, a multi-sampling ion chamber to measure energy loss, and a high-purity germanium detector to identify isomer decays and calibrate the system. We discuss the simulation and performance of HEIST using a beam centered around ¹⁹⁷Pb at about 75 MeV/A. With heavy nuclei at this energy, the beam is not fully stripped, and multiple charge states of each isotope can be present. This is one of the largest sources of contamination when trying to uniquely identify the beam. In this talk, we examine the simulation of beam production, including charge state distributions, and compare the simulation to the experimentally determined performance of HEIST. 

    

Detector characterization for particle-gamma coincidences at the Super-Enge Split-Pole Spectrograph (SE-SPS)

Highly efficient 2”x2” and 3”x4” CeBr3 gamma-ray detectors are currently being tested at Florida State University to arrange them in a modular array for particle-gamma experiments at the Super-Enge Split-Pole Spectrograph (SE-SPS). The coincidence timing between the anodes of the focal plane detection system and the  detectors has already been established with a 228Th calibration source. Furthermore, we characterized the CeBr3 detectors determining their energy as well as prompt timing resolution. To add to the ancillary detector systems at the SE-SPS, four Passivated Implanted Planar Silicon (PIPS) detectors of different thicknesses were also tested. Eventually, these are envisioned to be used for internal conversion electron detection. An overview of the different tests and results will be given.

    

Current Development and Status of the CHIPTRAP Penning Trap Mass Spectrometer

The Central Michigan University High Precision Penning Trap mass spectrometer (CHIP-TRAP) is being constructed to perform precise mass measurements with stable and long-lived isotopes. Applications include electron capture decay Q value determinations for ¹⁶³Ho and ⁷Be with applications to neutrino physics. CHIP-TRAP employs two external ion sources: a Penning Ion Trap (PIT) source that can ionize gaseous samples, and a Laser Ablation Source (LAS) for solid target materials. After production, ions are transported at 1 keV to an MR-TOF mass separator that will be used to isolate ions of different m/q before being transported to the Penning traps. The CHIP-TRAP will have two hyperbolic precision measurement traps for simultaneous cyclotron frequency comparisons with single ions of different species. It will also employ a cylindrical capture trap for elimination of contaminant ions. All three traps will be situated in a 12 T magnetic field and maintained at 4 K temperature using a pulse tube cryocooler. Currently the capture trap has been installed, and commissioning via image charge detection of ions in the trap is underway. In this presentation, we will provide an update on the operation of the ion sources, capture trap, cryocooling system and initial commissioning of the MR-TOF.

    

Development towards 53Mn Accelerator Mass Spectrometry Capabilities at the University of Notre Dame

Accelerator Mass Spectrometry (AMS) with ⁵³Mn has wide-reaching applications. Initially developed as a geological chronometer, ⁵³Mn has more recently been used to search for evidence of recent supernovae events, and has been proposed as a proxy to monitor the variation in the galactic cosmic ray spectrum over time. The low level detection of this isotope is challenging as it requires positive identification from the stable isobar ⁵³Cr which is also present within sample material. Very few facilities around the world are capable of separating and detecting this rare isotope, therefore prompting an investigation into current capabilities. 

At the University of Notre Dame’s Nuclear Science Laboratory (NSL), a 10 MV tandem accelerator and a Browne-Buechner Spectrograph operated in gas-filled mode with ΔE vs. position detection was used to isolate ⁵³Mn from ⁵³Cr. Samples covering ranges of ⁵³Mn/⁵⁵Mn=10^-8-10^-10 and natural manganese were measured for the first time at the NSL establishing an initial detection limit of ⁵³Mn/⁵⁵Mn=2x10^-11. Descriptions of experimental settings, analysis of the results, and further explorations will be presented.   

Testing of the St. Benedict Gas Catcher and Extraction System

Nuclear beta decays provide a unique avenue for testing the electroweak part of the Standard Model through precision measurements. Physics beyond the Standard Model would manifest itself in these transitions through a variety of possible effects including a non-unitarity of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. This effect can be probed for via measurements of the beta-neutrino angular correlation parameter in superallowed mixed decays. In order to study the isotopes of interest, a continuous beam of reaction products must be stopped, bunched, and transported with energies on the keV scale to an ion trap where a detector system can observe the beta decays. To that end, the Superallowed Transition Beta-Neutrino Decay Ion Coincidence Trap (St. Benedict) is currently under construction at the University of Notre Dame Nuclear Science Laboratory. The testing results of the St. Benedict gas-catcher cell, and commissioning of its ion extraction system, with a near 100% transport efficiency for the radio-frequency carpet within a pressure range of 0.75-5 mbar, will be presented.   

Commissioning of the RFQ Cooler and Buncher for St. Benedict

Unique insight into the electroweak part of the Standard Model can be found through precision measurements of nuclear beta decays. Non-unitarity of the Cabibo-Kobayashi-Maskawa (CKM) quark mixing matrix would be indicative of physics beyond the Standard Model. Measurements of the beta-neutrino angular correlation parameter for superallowed mixed mirror beta decays can be used to probe the unitarity of this matrix. The Superallowed Transition Beta-Neutrino Decay Ion Coincidence Trap (St. Benedict) is currently under construction at the Nuclear Science Laboratory (NSL) at the University of Notre Dame to improve the accuracy of the V_ud CKM matrix element. St. Benedict is comprised of several beam manipulating devices including a gas catcher, radiofrequency carpet, radiofrequency quadrupole (RFQ) cooler and buncher, and a measurement Paul trap. In order to make measurements at the needed precision, a bunch of ions with a well defined energy and emittance are required. To this effect, an RFQ cooler and buncher, following the design of such a device used for the NSCL EBIT, is currently being commissioned. The off-line commissioning setup consists of a thermionic emission source of potassium ions which sends beam through the RFQ where it is bunched and subsequently measured on a micro channel plate detector. With this system we are able to transport DC beam with 80% efficiency and obtain bunches with an 80 ns full-width-half-maximum. Progress on the off-line commissioning of the radiofrequency cooler and buncher will be presented.