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Register a new userDevelopment of an $alpha$-ToF detector for correlated measurement of atomic masses and decay properties
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We have developed a novel detector, referred to as an $alpha$-ToF detector, for correlated measurements of atomic masses and decay properties of low-yield, short-lived radioactive isotopes using a multi-reflection time-of-flight mass spectrograph. By correlating measured time-of-flight signals with decay events, it will be possible to suppress background events and obtain accurate, high-precision mass values even in cases of very low event rates. An offline test of the $alpha$-ToF detector has shown that the time-of-flight detection efficiency for 5.48~MeV $alpha$-rays is more than 90% and yields a time resolution of 251.5(68)~ps and an energy resolution of 141.1(9)~keV. Using a two-dimensional spectrum of the correlated $alpha$-ray energy and time-of-flight, the $alpha$-rays from mixed $alpha$ sources could be fairly well resolved.
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The atomic masses of the isotopes 206,207Ra have been measured via decay-correlated mass spectroscopy using a multi-reflection time-of-flight mass spectrograph equipped with an {alpha}-TOF detector. The Ra isotopes were produced as fusion-evaporation products in the 51V+159Tb reaction system and delivered by the gas-filled recoil ion separator GARIS-II at RIKEN. The {alpha}-TOF detector provides for high-accuracy mass measurements by correlating time-of-flight signals with subsequent {alpha}-decay events. The masses of 207gRa and 207mRa were directly measured using a multi-reflection time-of-flight mass spectrograph equipped with an {alpha}-TOF detector. A mass excess of ME = 3538(15) keV/c2 and an excitation energy of Eex = 552(42) keV were determined. The {alpha}-decay branching ratio of 207mRa, b{alpha} = 0.26(20), was directly determined from decay-correlated time-of- flight signals, and the reduced alpha width of 207mRa was calculated to be {delta}2 = 50+62-41 keV from the branching ratio. The spin-parity of 207mRa was confirmed to be J{pi} = 13/2 from decay correlated mass measurement results.
The photoneutron source (PNS, phase 1), an electron linear accelerator (linac)-based pulsed neutron facility that uses the time-of-flight (TOF) technique, was constructed for the acquisition of nuclear data from the thorium molten salt reactor(TMSR) at the Shanghai Institute of Applied Physics (SINAP). The neutron detector signal, with the information on the pulse arrival time, pulse shape, and pulse height, was recorded by using a waveform digitizer (WFD). By using the pulse height and pulse-shape discrimination (PSD) analysis to identify neutrons and $gamma$-rays, the neutron TOF spectrum was obtained by employing a simple electronic design, and a new WFD-based DAQ system was developed and tested in this commissioning experiment. The developed DAQ system is characterized by a very high efficiency with respect to millisecond neutron TOF spectroscopy
An electrostatic time-of-flight detector named E-MCP has been developed for quick diagnostics of circulating beam and timing measurement in mass spectrometry at the Rare-RI Ring in RIKEN. The E-MCP detector consists of a conversion foil, potential grids, and a microchannel plate. Secondary electrons are released from the surface of the foil when a heavy ion hits it. The electrons are accelerated and deflected by 90$^circ$ toward the microchannel plate by electrostatic potentials. A thin carbon foil and a thin aluminum-coated mylar foil were used as conversion foils. We obtained time resolutions of 69(1) ps and 43(1) ps (standard deviation) for a $^{84}$Kr beam at an energy of 170 MeV/u when using the carbon and the aluminum-coated mylar foils, respectively. A detection efficiency of approximately 90% was obtained for both foils. The E-MCP detector equipped with the carbon foil was installed inside the Rare-RI Ring to confirm particle circulation within a demonstration experiment on mass measurements of nuclei around $^{78}$Ge produced by in-flight fission of uranium beam at the RI Beam Factory in RIKEN. Periodic time signals from circulating ions were clearly observed. Revolution times for $^{78}$Ge, $^{77}$Ga, and $^{76}$Zn were obtained. The results confirmed successful circulation of the short-lived nuclei inside the Rare-RI Ring.
We have developed MICROMEGAS (MICRO MEsh GASeous) detectors for detecting {alpha} particles emitted from an 241-Am standard source. The voltage applied to the ionization region of the detector is optimized for stable operation at room temperature and atmospheric pressure. The energy of {alpha} particles from the 241-Am source can be varied by changing the flight path of the {alpha} particle from the 241 Am source. The channel numbers of the experimentally-measured pulse peak positions for different energies of the {alpha} particles are associated with the energies deposited by the alpha particles in the ionization region of the detector as calculated by using GEANT4 simulations; thus, the energy calibration of the MICROMEGAS detector for {alpha} particles is done. For the energy calibration, the thickness of the ionization region is adjusted so that {alpha} particles may completely stop in the ionization region and their kinetic energies are fully deposited in the region. The efficiency of our MICROMEGAS detector for {alpha} particles under the present conditions is found to be ~ 97.3 %.
A high-performance time-of-flight (TOF) MRPC wall is being built for the CBM experiment at FAIR for charged hadron identification. The detector control system for the TOF system will be based on EPICS. All components like power supplies for low and high voltages, power distribution boxes, gas control and front-end electronics (FEE) are controlled and monitored. In a test, called mini-CBM, all these functionalities are implemented and tested. For monitoring the detector environment and the status of the front-end electronics, a slow control application is implemented based on IPbus, which is an FPGA-based slow control bus used for the TOF data acquisition system. In addition to the functions of control and monitoring, exception handling and data archiving services are implemented as well. This system has been fully verified in beam tests in 2019 at GSI.
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