SPS electron slow extraction First studies of slow

SPS electron slow extraction First studies of slow extraction of electron beam from the SPS Y. Dutheil, M. A. Fraser, B. Goddard, J. Prieto, F. Velotti TE-ABT-BTP 03/02/2018 SPS electron slow extraction 2

Outline Introduction • Injection study • Extraction study • Conclusion • 03/02/2018 SPS electron slow extraction 3

Introduction • Slow extraction of electron at 10 Ge. V Experiments requires particles at up to 200 MHz and O(1 -10) e-/b [1] • Beam dynamics is dominated by synchrotron radiation Although some other facilities have been using slow extraction of electron beam, never has it been done at such high energy Closest study on HERA [2] for slow extraction of electrons at 15 -25 Ge. V. • • “Calculations and simulations show that the energy loss per turn in HERA is too large to enable the use of the second method. ” (read longitudinal drift out of the bucket). Propose to use a ramp of the tune towards the resonance for extraction [1] S. Stapnes, https: //indico. cern. ch/event/644287/contributions/2758574/ [2] M. Gentner, D. Husmann, P. Nghiem, J. Payet, A. Tkatchenko ELFE@DESY: SLOW EXTRACTION FROM HERA , 1997 [0] ELFE@DESY Conceptual design Report [0] https: //www. nikhef. nl/pub/projects/elfe/ and http: //hbu. home. cern. ch/hbu/Elfe. html 03/02/2018 SPS electron slow extraction 4

Injection study • • Beam produced at 3 Ge. V in 200 ns pulses fills 40 buckets with a 200 MHz RF system Alexej mentionned 100 ns train spacing for injection Momentum spread <1 Me. V Normalized transverse emittance ~10μm [1] Communication with Alexej Grudiev on 29/01/2018 03/02/2018 SPS electron slow extraction 5

Injection equilibrium emittance • Equilibrium emittance from MADX at 3 Ge. V with regular optics. Horizontal Vertical Longitudinal Damping time (s) 14 14 7 Equilibrium emittance (π μm) 0. 0021 0 1. 70 • U 0=0. 009667 Me. V/turn • Damping times are too long to be relied on for the injection scheme 03/02/2018 SPS electron slow extraction 6

Injection layout SPSLNINS 0086 03/02/2018 SPS electron slow extraction 7

Injection trajectory : ongoing • Trajectory of injection should follow extracted beam trajectory. QDA. 61910 MSEs 03/02/2018 SPS electron slow extraction 8

Extraction equilibrium emittance • Equilibrium emittance from MADX at 10 Ge. V with regular optics Horizontal Vertical Longitudinal Damping time (s) 0. 38 0. 19 Equilibrium emittance (π μm) 0. 023 0 5. 4 • U 0=1. 193419 Me. V/turn 03/02/2018 SPS electron slow extraction 9

Extraction layout in LSS 1 Magnetic dipole for extraction bump Magnetic septum Electric septum SPSLNIN 0051 03/02/2018 SPS electron slow extraction 10

Extraction scheme • Extraction scheme derived from proton simulations by L. Stoel. • • • Adequate for first checks Slow extraction on third order resonance driven by a sextupole. Machine optics fixed, no tune sweep Zero chromativity Preliminary : single virtual sextupole in LSS 2, upstream of MBB. 21550 Dx=0. 13 m and 227 deg horizontal phase advance upstream the electric septum Preliminary : dispersion is close to zero and particles drift in resonance “probably” due to amplitude detuning. 03/02/2018 SPS electron slow extraction 11

Extraction phase space Simulation of extracted particle in purple and non extracted particles in green. Number of turns to extraction is random and different for every particle (with different random generator seed). 03/02/2018 SPS electron slow extraction 12

Extracted phase space • Simulation with 1000 particles showed at the electric septum. Particles in orange are kicked by the septum and extracted while their position on the 3 previous turns are showed in green. In purple is the position of the particles during the 1000 turns before extraction. No machine parameters are changed and only quantum excitation brings particles in and out of resonance. Extraction efficiency is far from optimized. Is efficiency important ? Is extracted beam emittance important ? 03/02/2018 SPS electron slow extraction 13

New magnetic septum Extracted trajectories MKPs QDA. 11910 MSIs Extracted trajectories are in red while the 3 turns leading to extraction are showed in green. Blue trajectories correspond to circulating beam. Electric septum is at s=0 m. Injected and circulating FT beam at 14 Ge. V with margins is showed in grey. Zoom around electric septum showing the distance between the septum foil and the circulating FT beam Sizing • Electrostatic septum 1. 5 m long and 3. 3 MV/m to provide 0. 5 mrad kick at 10 Ge. V • Magnetic septum 1. 5 m long and 100 m. T to provide 4. 5 mrad. Should be feasible with a blade of 5 mm 03/02/2018 SPS electron slow extraction 14

Extraction machine trajectory • Orbit bump in LSS 1 using one existing corrector and 3 new Electrostatic septum Extraction channel MKPs 03/02/2018 Apertures are showed in black and the origin is taken at the entrance of the electric septum. SPS electron slow extraction 15

Conclusion • • Injection of 200 ns beam seems possible from longitudinal simulation. Slow extraction with bunched beam seems to be working. • • • Design of injection to be done • • Precise extraction scheme to be investigated. In particular: is the quantum excitation sufficient or would something need to push the beam on the resonance during extraction? How to reach the very low intensity per bunch crossing required (1 -10 electrons). Study in particular effects of magnet/optics ripples. trajectories and sizing of a fast injection kicker A CERN workspace, a SLACK and a gitlab repository were setup to work collaboratively on this. • • • cern. ch/test-ESEWG esewg. slack. com/messages gitlab. cern. ch/ydutheil/ESEWG 03/02/2018 SPS electron slow extraction 16

Thank you 03/02/2018 SPS electron slow extraction 17