PS-ESS and LEBT State of the art Lorenzo Neri Istituto Nazionale di Fisica Nucleare Laboratori Nazionali del Sud

Proton Source for ESS Final design: - Fine RF study - Optimized matching transformer - Updated magnetic system - New magnetic shielding - Fully integrated mechanical design

Fine RF study Cavity frequency domain study with real dimensions an real materials: Copper chamber cylinder ARMCO walls Two Boro Nitride insulators disk Aluminum wave guide Extraction hole Optimization of all geometrical parameters of the matching transformer: Step width, height, length, number

Flexible magnetic system InjectionChamberExtraction Low magnetic field in the extraction region to prevent emittance growth Low magnetic field in the injection region to prevent ECR and plasma formation inside wave guide DONE NEW

New magnetic shielding Optimum magnetic shielding and Electro-Magnetic coupling inside the plasma chamber Magnetic field Electric field E-M energy density Injection Chamber Extraction

Final Source Design

Upgrade of extraction system Final design: - Improved ground shielding of the beam region - Improved emptying cavity gap between electrodes - Single alumina - New triple point design (metal-vacuum-alumina)

electrodes chopper Solenoid Pro and Con: + Faster beam rise time by decreasing SCC in the LEBT before the beam pulse propagation - Perfectly knowing of beam characteristics is required - High sensibility to beam condition - High divergence region => difficult deflection - High electric field in a not clean region - Complex beam stop design inside the solenoid tube - Possible interaction with diagnostics before the solenoid Chopper inside extraction test Instr.

Beam formation study Potential [V] Plasma meniscus 3D PIC simulation

LEBT optical elements Solenoid assembled with steerer Chopper assembled with TMP RFQ collimator used to dump the chopped beam Repelling electrode Cooling system will be dimensioned for full beam power (300W)

LEBT Beam Instrumentation Courtesy of Benjamin Cheymol

Chopper electronics Electronics developed by INFN-LNS for SPIRAL 2 project already tested at CEA-IRFU Low voltage control electronics High voltage Main important devices already ordered: HV power supply HV switch RF vacuum connection

Beam Pulse formation Low emittance growth and Twiss parameters coupled to RFQ acceptance are required Estimate and reduce the rise time Estimate the charge that must be cut by MEBT-Chopper Estimate the fall time Highly divergent beam during source startup must be stopped ESS requirements:  14 Hz repetition rate  2.86 ms beam width  Emittance < 0.2 π∙mm ∙ mrad  100 ns rise and fall time

Pressure along LEBT Cylinder: RFQ Cylinder 6mm Ø 9.5mm long Cone 40 mm long Cylinder: LEBT -55% Constant pressure along all the LEBT included collimator cone

Space Charge Compensation 100 mA H + beam in hPa of H 2 gas Beam Gas Beam Line SCC creation time scale

Steady state Magnetic field Output of Axcel extraction system simulation …to match RFQ twiss parameters Optimum magnetic configuration have been found with TraceWin beam transport simulation… SCC=98%

Ions in the Beam Chopper-OFF transition Electrons in Beam-Plasma SCC can’t be preserved during transition Chopper ON Chopper OFF Radial drift ≈ 28mm 15 ns 1m with reduced SCC

Chopper-OFF transition Chopper ON Chopper OFF 1 meter with reduced SCC means high SCC sensitivity => Low transmission fraction until high SCC is reacted

Chopper-OFF transition H + beam in H 2 gas 95% after 740 ns 15% after 430 ns 190 W/MeV MEBT-Chopper is required Ar residual gas 1 meter with reduced SCC means high SCC sensitivity => Low transmission fraction until high SCC is reacted

PROTON SOURCE : - Flexible magnetic system √ - RF coupling √ - Mechanical design √ - Upgraded extraction √ - Chopper inside extraction REJECTED √ - Beam formation study IN PROGRESS (optional) LEBT : √ - Optical elements designed √ - Chopper electric prototype already tested √ - RFQ twiss parameters satisfied √ - Beam rise and fall time predicted √ - Diagnostics IN PROGRESS (required)

Thanks for the attention Comments are welcome Thanks to: D.Mascali, S.Gammino, L.Celona, G.Torrisi, L.Allegra, A.Caruso, A.Ponton