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Register a new userA large Bradbury Nielsen ion gate with flexible wire spacing based on photo-etched stainless steel grids and its characterization applying symmetric and asymmetric potentials
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Bradbury Nielsen gates are well known devices used to switch ion beams and are typically applied in mass or mobility spectrometers for separating beam constituents by their different flight or drift times. A Bradbury Nielsen gate consists of two interleaved sets of electrodes. If two voltages of the same amplitude but opposite polarity are applied the gate is closed, and for identical (zero) potential the gate is open. Whereas former realizations of the device employ actual wires resulting in difficulties with winding, fixing and tensioning them, our approach is to use two grids photo-etched from a metallic foil. This design allows for simplified construction of gates covering large beam sizes up to at least 900,mm$^2$ with variable wire spacing down to 250,textmu m. By changing the grids the wire spacing can be varied easily. A gate of this design was installed and systematically tested at TRIUMFs ion trap facility, TITAN, for use with radioactive beams to separate ions with different mass-to-charge ratios by their time-of-flight.
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This investigation presents a new experimental determination of the reflectivity of 128 nm scintillation photons off stainless steel. The experiment took place in the TallBo dewar facility at Fermilab. The data were obtained using a detector that is sensitive to photons falling on its front face but is insensitive to photons falling on its back face or its sides. By comparing the ratio of photons per track from tracks that illuminate the front face of the detector to those that cross the back side with a simulation of the experiment where the reflectivity can be varied, a value of the reflectivity was determined. The reflectivity for the SA-240-304L stainless steel alloy off which the scintillation photons reflect in the TallBo dewar as found by this experiment is R = 0.674 +/- 0.038. The experiment is not sensitive to the differences between specular and diffuse reflections.
The data acquisition system is based on ROOT and waveform digital technology, including neutron detector, waveform digitizer, PCI card, optical fiber, computer, reaction target device, stepper motor, data acquisition software and control target software. It achieves to acquire and record the waveform information of signal measured by the detector using a waveform digitizer. The specific target position is changed by the stepper motor which is remotely controlled by the data acquisition software and control target software. It is implemented by the exchange of information between the data acquisition software and the control target software. The system realizes to automatically open files and change targets at fixed intervals. It is capable of data compression by removing the data those are not signals, and automatic alarm when the beam is lost.
This paper describes the design and the construction of the stainless steel tank of the JSNS$^2$ detector. The leakage was examined using water and gas after the construction. The new sealing technique with liquid gasket was developed, and its sealing capability was evaluated quantitatively. The result shows over 5 times better value than the tolerance level of leakage.The acceleration measurement during the transportation of the tank shows adequate robustness.These tests prove that the stainless steel tank is feasible to use the real experiment.
To ensure compliance with the experimental requirement for ultra-low background, in this study the radioactivity of stainless steels manufactured by smelting is thoroughly investigated. Raw materials, stage samples, and commercial samples are investigated by glow discharge mass spectrometry (GDMS) and/or with high-purity germanium detectors (HPGe) at both the ground level and/or the China Jinping Underground Laboratory. Custom-made stainless steel samples are found to have radioactivity levels comparable to those in other low-background experiments. The comprehensive results regarding the radioactivity level in materials to be used in the proposed Jinping Neutrino Experiment are reported.
The ultracold neutron (UCN) source at Los Alamos National Laboratory (LANL), which uses solid deuterium as the UCN converter and is driven by accelerator spallation neutrons, has been successfully operated for over 10 years, providing UCN to various experiments, as the first production UCN source based on the superthermal process. It has recently undergone a major upgrade. This paper describes the design and performance of the upgraded LANL UCN source. Measurements of the cold neutron spectrum and UCN density are presented and compared to Monte Carlo predictions. The source is shown to perform as modeled. The UCN density measured at the exit of the biological shield was $184(32)$ UCN/cm$^3$, a four-fold increase from the highest previously reported. The polarized UCN density stored in an external chamber was measured to be $39(7)$ UCN/cm$^3$, which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of $sigma(d_n) = 3times 10^{-27}$ $ecdot$cm.
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