Investigations of the output energy deviation and other parameters during commissioning of the four-rod radio frequency quadrupole at the Fermi National Accelerator Laboratory

Abstract

After 30 years of operation, the Cockcroft-Walton based injector at the Fermi National Accelerator Laboratory has been replaced by a new beam line including a dimpled magnetron 35 keV source in combination with a 750 keV four-rod radio frequency quadrupole (RFQ). The new injector is followed by the existing drift tube linac. Prior to installation, a test beam line was built which included the magnetron source and the four-rod RFQ with a number of beam measurement instrumentation. The first beam test with the RFQ showed an output energy deviation greater than 2.5%. Other problems also showed up which led to investigations of the output energy, power consumption and transmission properties using rf simulations which were complemented with additional beam measurements. The sources of this deviation and the mechanical modifications of the RFQ to solve this matter will be presented in this paper. Meanwhile, the nominal output energy of 750 keV has been confirmed and the new injector with the four-rod RFQ is in full operation.

Cs-doped Mo as surface converter for H−/D− generation in negative ion sources: First steps and proof of principle

“…For example, in the frame of neutron therapy [1], for spallation neutron sources [2] as well as for neutral beam injection (NBI) systems on LHD [3]. For ITER, H -/D -NBI systems based on the small [4,5] and "half-size" [6,7] IPP prototype sources will be used.…”

Slip-stacking Dynamics for High-Power Proton Beams at Fermilab

“…The NOvA experiment, a long-baseline neutrino oscillation measurement using the NuMI beamline, is currently the primary user of the Fermilab proton complex. [19][20][21]. Attached to the RFQ injector are two identical magnetron-based sources.…”

“…Model of the new RFQ-Injector. The beam begins in one of two H − magnetrons, travels to the RFQ through the LEBT solenoids, accelerates to 750 keV in the RFQ, and matches to the Linac with the MEBT [19]. The Linac accelerates the 750 keV H − beam to 116.5 MeV using a 75m sequence of five drift-tube linac (DTL) modules and accelerates from 116.5 MeV to 400 MeV using a 64m sequence of seven side-coupled linac (SCL) modules.…”

Commissioning and Operation of the FNAL Front end Injection Line and Ion Sources.

“…The RFQ that replaced the Cockcroft-Walton Preaccelerators due to its smaller footprint and higher energy efficiency is shown with its vacuum tank opened in Figure 14. A rod style RFQ manufactured by A. Schempp [6] was chosen and was delivered for initial testing in August, 2011. The important parameters are shown in Table 1.…”

“…End plates had been installed in the upstream and downstream entrances with ¾" apertures to limit RF leakage from the RFQ as shown in Figure 21a. Once this end plate was removed from the downstream end of the RFQ, the beam energy from the RFQ was measured to be 757 keV +/-2.5 keV with 167 kW of power in the RFQ [6]. The RFQ is operated without this end plate, see Figure 21c.…”