E-lens related beam studies Xiaofeng Gu, Wolfram Fischer, Peter - PowerPoint PPT Presentation

E-lens related beam studies Xiaofeng Gu, Wolfram Fischer, Peter Thieberger, Toby Miller, Zeynep Altinbas , Michiko Minty 1

APEX Summary 1. had 3 stores with 56 bunches, concentrated in 2 trains with large gap in the middle; all 3 stores were lost due a permit pull from the Blue abort kicker 2. the first store allowed taking an electron beam profile measurement with the YAG screen, showing a hollow beam; electron beam shape changes were observed with changes in the electron beam energy and current 3. the second store was to short for any measurement 4. the third store allowed for scanning the horizontal and vertical positions of the hollow electron beam while observing the backscattered electron beam signal 5. a full horizontal scan (showing 2 maxima), a full vertical scan (showing 1 maximum), and a half horizontal scan (showing 1 maximum) at a higher vertical position were completed - the last scan is incomplete due the Blue abort kicker permit pull 2

Hollow Cathode 3

profile vs e-beam current 1. Asymmetry: caused by bending magnetic field? Or from source? 2. More distortion with higher current saturation I=308mA I=820mA I=1050mA E=5kV E=5kV E=5kV 4

Horizontal profile vs e-beam current saturation 5

profile vs e-beam energy 1. less distortion with higher voltage saturation I=1050mA E=5kV I=1050mA I=1050mA I=1050mA E=5kV E=6kV E=7kV 6

Horizontal profile vs e-beam energy saturation 7

BPM alignment (April 4) Horizontal Vertical 8

Alignment via Lisa Scan (Wolfram) 1. Two local peaks were found via moving ion beam (Ruthenium, 0.2mm step, 40mA DC beam) for each plane; 1 st : horizontal Scan. 2 nd : vertical scan, moved to hollow center (X=1.6mm); 3 rd : horizontal scan with Y = 1mm, 2. interrupted by beam abort 3. Hpeak1>Hpeak2: could contributed by non-uniform e-beam intensity, U shape e-beam trajectory and angle; 4. Vpeak2>Vpeak1: contributed by longer vertical distance to the eBSD, non-uniform e-beam intensity or angle; moving e-beam could be better. 9

Hollow beam size inside superconducting magnet • HPeak2-Hpeak1 = 3mm • Vpeak2-Vpeak1 = 3.2mm • Ring Center D= 3.071 mm • Area inside cold magnet: 4.68 mm 2 • Intensity for 1050mA: 224mA/mm 2 10

Notes 1. After bpm electronics repairing, e-beam was aligned to ion beam very well, even after some orbit shifts during collapsing separation bump; 2. electron beam shape distortion caused by higher current could cured by higher electron beam energy; reduce e-beam intensity during propagation is another method, will try this later via changing magnetic field; will try whether bending field effect on beam profile; will find out whether ion beam could affect beam profile->the third alignment method if yes (Peter); 3. The eBSD could be used as hollow beam alignment; Angle alignment will be done next time, via minimized the valley value; 4. Need pay more attention to SC cooling kicker with this 56x56 pattern. Camera exposure time is too long and didn’t do background substraction. 5. 11