Pasta – an RF Phase Scan and Tuning Application

SNS machine status report

“…The phase and amplitude set points can be derived by comparing the measurements to model predictions [11]. The PASTA method also gives good results, and we have observed good agreement between the two methods [9].…”

“…A model-based fit is then performed to three phase-scan "signatures" simultaneously to obtain the RF amplitude, relative phase of the beam and the RF, and the input energy. There is a good agreement between the two methods [9]. The PASTA method has the advantage of using non-interceptive BPMs, in contrast to the acceptance scan method, where the beam pulse width and current must be reduced when inserting the ED/FCs for the acceptance scan method.…”

“…The second technique is based on the "phase-scan signature matching" approach [8], where the beam phase from a single BPM, or the phase difference between two BPMs downstream of a DTL tank, are measured as a function of the tank phase and amplitude and compared with model simulations (the SNS implementation of the algorithm is dubbed PASTA [9]). Figure 2 shows an example of the scan for DTL tank 1, in which three sets of beam phase vs. tank phase were measured.…”

RF amplitude and phase tuning of J-PARC DTL

“…Then, we have determined the RF set-point so that we can reproduce the overall shapes of the simulated phase-scan curves instead of using the location of a specific intersection point. This tuning strategy is the so-called "phase-scan phase signature matching" [9], and the same scheme has been adopted in SNS [10,11]. According to this change of analysis procedure, the scanning range of the phase is widened from that originally planned to enable the effective signature matching.…”

The Spallation Neutron Source Beam Commissioning and Initial Operations

“…A linearized beam response approximation implementation of this approach is referred to as the Delta-T method [20]and has been used at SNS [21].This technique works well if the initially scanned RF phase is within about 5-10 degrees of the targeted synchronous phase and the amplitude is within 10 percent of the desired setting. A more general phase scan technique is the signature matching method [22,23]. This method does not use linear approximations and is useful over a wider RF phase range.…”