Applied Physics Researches Division (APRD)

Posts made in March, 2019

Group 2014-2019 investigations

Posted by on Mar 28, 2019

Group 2014-2019 investigations

Development of a new type of Vibrating Wire Monitor (VWM), which has two mechanically coupled wires (vibrating and target), is presented. The new monitor has a much larger aperture size than the previous model of the VWM, and thus allows us to measure transverse beam halos more effectively. A prototype of such a large aperture VWM with a target wire length of 60 mm was designed, manufactured, and bench-tested. Initial beam measurements have been performed at the Fermilab High Intensity Neutrino Source facility, and key results are presented. Fig. 1. (a) Photo of the Large Aperture Vibrating Wire Monitor (LA-VWM). (b) Beam profile, measured by the LA-VWM in the horizontal direction at the Fermilab High Intensity Neutrino Source facility. Measurements of secondary particles/photons reflected/generated from an oscillating wire in synchronism with the wire oscillation frequency are proposed. The differential signal on wire maximal deviations at oscillation process can provide a fast signal proportional to beam profile gradient. Idea of using such “Resonant Target” for beam transverse gradient profiling was tested with lightening the oscillating wire by a laser. Fig. 2. (a). Layout of experiment: 1 – vibrating wire of VWM with wire length 80 mm, 2 – wire oscillation generating magnet poles, 3 – laser, 4 – photodiode. (b) Forward and backward scan of the vibrating wire sensor. Red line – differential signal from photodiode at ultimate positions of wires during oscillations. Green line – averaged signal of 1000 measurements of photodiode at ultimate positions of wires, Blue line – vibrating wire oscillation frequency also depends on reflecting on wire photon numbers. Proton/ion beams of multiple charge/mass ratios can be very complex. Orthogonal X-Y projections are often inappropriate to represent these profiles. An array of vibrating wires, rotating around the beam axis is under development. The mechanical implementation is described. An algorithm to reconstruct the profile is proposed. The tradeoffs between the number of wires, the rotation angles, the response time and the profile resolution are discussed. Fig. 3. (a). Numerals indicate: (1) – measured beam, (2) –frame of monitor, (3) – vibrating wires, (4) –support flange with gear teeth on the flange rim, (5) – loading gear with shaft translated rotation, (6) inclination axis supporting lips, (7) – gearbox-transmitter translate inclination axis rotation to the shaft (8). (b). Test distribution of the beam to be measured. Two types of neutron monitors with fine spatial resolutions are proposed based on vibrating wires. In the first type, neutrons interact with a vibrating wire, heat it, and lead to the change of its natural frequency, which can be precisely measured. To increase the heat deposition during the neutron scattering, the use of gadolinium layer that has the highest thermal neutron capture cross-section among all elements is proposed. The second type uses the vibrating wire as a “resonant target.” Besides the measurement of beam profile according to the average signal, the differential signal synchronized with the wire oscillations defines the beam profile gradient. The monitor’s spatial resolution is defined by the wire’s...

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