Beam instrumentation for the SSC RFQ

Abstract

II. DESCRIPTION OF THE BEAM ,, A detailed descriptio:aof the SSC RFQ beam instrumenta-INSTRUMENTS tion is presented. Most of the instrumentation is located in the RFQ end walls. The upslream end wall contains a segmented The entrance endwall contains the segmented aperture and 4 Faraday cup, a segmented aperture and a wire scanner. The Faraday cup whichcan be used as separate instruments or as a down stream end wall contains a segmented aperture and wire system with 1mm spacing between them. The segmented secscanner. Two current toroids are used to measure the transmis-t.ionsof each instrument can be monitoredindependently. sion through the RFQ. The output of the RFQ is a low emit-Beam positioning is accomplished by producing equal current tance, pulsed 2.5 Mev H"beam with peak current of 25mA and on ali four segments. By placing the aperture and Faraday cup maximum pulse length of 35 gs. Typical beam data are shown in the beam line at the same time, beam size and position can with the emphasis being on mstaunentation performance, be obtained. When the instrttmentsare at the beam line center, the operator can steer the beam into the RFQ by monitoring the I. INTRODUCTION current on the individual wedges. Once the segments have equal current values, the Faraday cup can be removed to allow The RFQ instnmaentationconsist bf two current toroids, a for beam transmission into the RFQ. A second aperture is used segmented Faradaycup, two wire scanners andtwo segmented m the exit end wall of the RFQ to define the maximum beam apertures. Ali of the instruments except the current toroids are size into the DTL matching section. The transmission through actuated instruments and mounted in the end walls. Of the two the RFQ is measured by two matched current toroids. A 195 current toroids one is up stream and one is down s_'eam of the mm OD toroid surrounds the ion source low energy beam RFQ. The toroids have been electrically matched to allow for transport and is mounted just upstream of the RFQ entrance proper transmissionmeasurements during commissioning. The end wall. A matched toroid is mounted in a temporary diagnoswire scanners are placed up and down stream of the RFQ to tic chamber at the exit of theRFQ. When the two current toroid measure the beam profile,and position information. Also up waveforms are superimposed, the ratio is the total current stream is the segmented aperture andthe segmented Faraday transmission through the RFQ as a function of time. The wire cup which will define a maximum beam size and measure the scanners located at both theentrance and exit end walls are beam position and current respectively. Down stream is a seg-designed to have three separate wires that are electrically isomented aperture which defines the beam size entering the Drift lated to cover X,Y,and 45°. The profile is measured by step-Tube Linac (DTL) matching section. Figure 1shows the RFQ ping the wire through the beam and recording the current on with the instrumentation mounted, each wire. By plotting the position and the measure...