Intrumentation HEL powering interlocks HEL main parameters today

Intrumentation, HEL powering, interlocks

HEL main parameters today Parameter Value or range Proton beam optics at HEL, b [m] 280 Length of interaction, L [m] 3 Desired transverse scraping (3 to 6 beam s), r [mm] (note that here geometric emittance = 3. 5 umrad) Electron beam current, I [A] 1. 1 – 2. 2 @ 7 Te. V 4. 3 – 8. 6 @ 450 Ge. V 5 Cathode diameter [mm] 8 to 16 Gun extraction and modulation voltage [k. V] 10 Cathode-ground voltage [k. V] 15 Collector voltage [k. V] in study Modulator rise time [ns] 200 Modulator repetition rate [k. Hz] 35 Magnetic field at gun [T] 0. 35 @ 7 Te. V to 4 @ 450 Ge. V Magnetic field at bend [T] 3. 5 Magnetic field at main [T] 3 @ 450 Ge. V to 5 @ 7 Te. V A. Rossi, International Review of the HL-LHC Collimation System, CERN, 11 -12 February 2019 2

Space Charge driven Instabilities A. Rossi, 7 th HL-LHC Collaboration Meeting, 13 -16 November 2017 CIEMAT Madrid sio n peak collector current [A 1/2] pre s ut c Wit § Measurements show that at low current density we could operate at 5 A (25 mm outer radius) with 4 T and a ~round beam § Compression (5 A to <4 mm outer radius) will increase space charge and may cause the electron beam profile to ovalise and tilt. om magnetic field in main solenoid (gun solenoid at 0. 2 T) ho CHG 1 B 25 cathode – 63 chamber § Current profiles scaling with indicate that we are in space charge dominated regime cathode-anode voltage [k. V 1/2] G. Stancari FNAL § Studies with 5 T / 5 A, and reduced beam pipe diameter (60 mm) show relative good results But space charge effects are not directly a show stopper! Rather, they might limit the maximum acceptable electron beam current and thus the cleaning efficiency O. Brüning, Chamonix Performance Workshop 2018 3

The system configuration ward recte i d e rc lly in radia d Fo s line x u l f netic g ory aject e e tr in -r Mag HL-L HC E-gun solenoid ons prot 00 ~ 40 mm BPMs integrated in vacuum chamber Main solenoids Collector Checking for diagnostics at collector room for BGC monitor Electrons are produced by the cathode of an e-gun. A system of superconducting solenoids cooled at 4. 5 K generates the magnetic field to tune de size and steer the trajectory of the electron ring. D. Perini, 8 th HL-LHC Collaboration Meeting, CERN, 15 -18 October 2018 4

Schedule § Assuming we want to operate the HEL in Run IV § Assuming HEL built as in-kind A. Rossi, International Review of the HL-LHC Collimation System, CERN, 11 -12 February 2019 5

Hollow Electron Beam Simulations Prof of HEL parameters § CST Particle Studio simulation of the Hollow Electron Lens to feedback to thermomechanical design (here shown for 7 Te. V ops) 5 Ax 15 k. V 5 T BINP A. Rossi, International Review of the HL-LHC Collimation System, CERN, 11 -12 February 2019 6

450 Ge. V circulating beam BINP A. Rossi, International Review of the HL-LHC Collimation System, CERN, 11 -12 February 2019 7

Beam Gas Curtain Monitor § Beam-Gas Fluorescence on target gas curtain § Looking at Ne and Ar as gas § Prototype to be installed in LHC Nitrogen gas jet test Moveable gauge measurement of the gas jet. This will be smaller in the interaction chamber. Courtesy of R. Veness, T. Dodington, H. Zhang, S. Udrea and BGC collaboration 8 th HL-LHC Collaboration meeting, 15 -16 October 2018 IBIC 2017 § Scaled version to be designed A. Rossi, International Review of the HL-LHC Collimation System, CERN, 11 -12 February 2019 8

BPMs § BPMs integrated in the vacuum chamber at the beginning of the first mail solenoid and at the end of the second. § First draft design to fit in space available § E-beam measurement: § for the moment we assume that it will work on the ramp-up or rampdown of the e-beam = 200 ns ramp during p-beam gaps § Circulating (p or ion) beam measurement: as in LHC § Questions still open: § Accuracy of relative positions considering that electronics will be different for 2 measurements. § Required 70 um (sigma at 7 Te. V = 0. 36 mm) 9

HEL schematics Electron gun (A) (8 -16 mm cathode) Modulator (35 KHz) Instrumentation BPMs Collector Overlap/transverse profile monitors BGC Gun solenoid (0. 3 to 4 T) Bending SC solenoids ~3. 5 T Main SC solenoids 3 to 5 T 10

Collector Electron gun 5 Ax 15 -20 k. V VCA Cathode Heater 10 Ax 40 V cathode grid anode + Control electrode -2 +2 k. V x 40 m. A – + + Anode modulator – VCA≤ 20 k. V, Ianode 35 k. Hz, 200 ns rise time VCO Anode/grid modulator 40 MHz – Cathode – – + Collector PC – Cathode PC + Anode modulator -3 KV High voltage (15 -20 k. V) low current (losses) VCA, Itube -15 k. V repeller High voltage (~15 k. V) High current VCA-VCO, Ibeam=5 A 0 -10 k. V 11

Location of new HEL in LHC Ring (P 4) HEL(B 2 e) HEL(B 1 i) ST 0676534_01 B 2 B 1 RB 44 RA 43 D 3 L 4 HEL(B 1 i) ACS ADT UJ 44 UA 43 19/10/2017 UL 44 US 45 1764989 v. 3 12 M. Gonzalez de la Aleja, Paolo Fessia A. Rossi, International Review of the HL-LHC Collimation System, CERN, 11 -12 February 2019 12

HEL integration in LHC M. Gonzalez de la Aleja, Paolo Fessia ST 0676534_01 . The beam to beam distance is 420 mm. The longitudinal available space is limited. Compact design 6