RFQ CAD Model Tolerance Studies Simon Jolly 2 nd May 2012

RFQ Tolerance Simulations Went back and retested 2 sets of simulations: –Offsetting top vane across between 10 microns and 1 mm, giving an approximation of a major vane assembly misalignment. –Pushing left vane in and out between +1 mm and –1 mm, giving an approximation of a minor vane assembly misalignment. Simulation parameters the same as before: –Still starting 10.9 mm long bunch at start of matching section. –0.25 pi mm mrad waterbag emittance. 02/05/12Simon Jolly, University College London2

RFQ Tolerance Studies Looking at several alignment/assembly tolerances: –Offsetting top vane to the left. –Pulling left vane in and out. –Offsetting tank 2 to the left. Tank 2 offset simulations are new: –Needed to rebuild Comsol model. –Can only produce field map for 200 micron offset or larger: below this the edge becomes too sharp and Comsol can’t model it. As well as looking at beam transmission, also looking at exit emittance: comparing exit screen to exit bunch (not the same). 02/05/12Simon Jolly, University College London3

500 micron Top Vane Offset: Geometry 02/05/12Simon Jolly, University College London4

CAD Models: Matching Sections 02/05/12Simon Jolly, University College London5

CAD Models: Lead Out/End Flanges 02/05/12Simon Jolly, University College London6

Beam Transmission: “Perfect” RFQ 02/05/12Simon Jolly, University College London7

Exit Emittance: “Perfect” RFQ 02/05/12Simon Jolly, University College London8

Left Vane Offset: 60 mA Transmission 02/05/12Simon Jolly, University College London9

Left Vane Offset: 60 mA Emittance 02/05/12Simon Jolly, University College London10

Top Vane Offset: 60 mA Transmission 02/05/12Simon Jolly, University College London11

Top Vane Offset: 60 mA Emittance 02/05/12Simon Jolly, University College London12

Tank 2 Offset: 60 mA Transmission 02/05/12Simon Jolly, University College London13

Tank 2 Offset: 60 mA Emittance 02/05/12Simon Jolly, University College London14

Beam Transmission: “Perfect” RFQ 02/05/12Simon Jolly, University College London15

Tank 2, 200 micron Offset 02/05/12Simon Jolly, University College London16

Tank 2, 500 micron Offset 02/05/12Simon Jolly, University College London17

Exit Emittance: “Perfect” RFQ 02/05/12Simon Jolly, University College London18

Tank 2, 200 micron Offset 02/05/12Simon Jolly, University College London19

Tank 2, 500 micron Offset 02/05/12Simon Jolly, University College London20

Conclusions Alignment tolerance much slacker than machining tolerance. Y-vane offset makes virtually no difference: why? X-vane offset more pronounced: –Pulling vane out decreases E-field AND increases resonant frequency: bad! –Pushing vane in increases E-field AND decreases resonant frequency: not as bad… Tank 2 offset much more significant: –200 micron offset still gives noticeable beam loss. –Can’t go smaller with current field map simulation… Exit emittance hardly changes: –Small emittance growth for X-vane pushed in (as Juergen predicted!). –Otherwise emittance unchanged, even for big beam loss… Exit bunch emittance tracks exit screen emittance, but (as expected) exit screen slightly larger. Now the code is written, exit bunch more reliable (although ~80% of particles). 02/05/12Simon Jolly, University College London21

Paper 1: RFQ Integrated Design Paper will cover modelling background for our integrated RFQ design method. This is mainly RFQSIM -> Inventor -> Comsol -> GPT -> Matlab, but also includes sections on bulk CAD design and electromagnetic/thermal simulations. Half written: just waiting for other people to fill in some sections: –Introduction –*Vane Modulation Parameter Generation (APL – RFQSIM) –*RFQ Mechanical Design (PJS) –Vane Tip Modulation CAD Design (SJ) –*Electromagnetic Cavity Simulations (SL) –*Thermal Modelling (SL) –Beam Dynamics Simulations (SJ) Field Mapping (SJ - Comsol) Particle Tracking in GPT (SJ) –Conclusions (SJ) 02/05/12Simon Jolly, University College London22

Paper 2: FETS RFQ Design Paper will cover all steps we went through to design FETS RFQ. Will refer to previous integrated design paper, so no need to describe methods again, but needs to include all information showing how much work we’ve done on the various aspects of the design. I will take as much as I can from the conference papers, but will need help filling in gaps as there are several things that have been presented at FETS meetings I couldn’t find in PAC/EPAC papers. Outline will be similar: –Initial parameter generation and design limitations (APL + RF/klystron) –Basic CAD design (PJS) –Cold model construction and bead pull (SJ/PJS) –Electromagnetic cavity simulations (SL) –Thermal simulations and squirt nozzle/cooling design (SL/PJS) –Vane tip CAD modelling (SJ) –Beam dynamics simulations, inc RFQSIM/CAD modelling comparison (SJ) –Final CAD design, including tuner design, RF feedthroughs etc and final RFQ parameter comparison (SJ/PJS/APL) –Anything else… As Juergen suggested, this paper should include everything but also refer to conference papers… 02/05/12Simon Jolly, University College London23

Paper 3: Fringe Fields/Tolerances Paper will cover all the “edge effects” that have come largely from the CAD modelling. Try to show how really starts to interfere on some of the “optimised” areas of the RFQ design. Juergen’s work on the effect on the beam energy spread from the matching section fringe field: I will run some simulations (suggestions please…). All the simulations I’ve done recently checking the alignment and machining tolerances. 02/05/12Simon Jolly, University College London24