Technological aspects of Electron Lenses, errors and control Vsevolod Kamerdzhiev for Fermilab Beam-Beam Compensation team LARP Mini-Workshop on Beam-Beam Compensation, July 2-4, 2007

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 2 Tevatron Electron Lenses TEL2 The TEL2 magnetic system consists of eight conventional solenoids, the 65 kG SC main solenoid, four short 8 kG and two long 2 kG SC dipole correctors.

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 3 Magnetic field measurements Short corrector 1, I = A Longitudinal pozition z, mm Magnetic field, kG Magnetic field quality along the electron beam path has been verified using 3D Hall probe in addition, a laser based technique was used to check the straightness of magnetic field lines in the main solenoid (<100  m).

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 4 Electron gun

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 5 Using the tube based modulator

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 6 First TEL2 e-beam Cathode current Collector current Modulator grid Trigger pulse Was improved to better than 5%

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 7 TEL1 e-current ripple 0.4 Hz 15 Hz ~1% variation

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 8 Using the Marx generator

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 9 Modulator vs Marx generator

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 10 Marx generator

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 11 TEL2 in pulsed mode (Marx)

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 12 TEL2 e-current ripple, timing jitter 60 Hz <1 % cure found fixed < 1ns now

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 13 Marx generator failure Schottky power

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 14 Emittance growth vs e-beam noise TEL2 Δε/Δt

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 15 Emittance growth vs e-beam noise TEL1

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 16

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 17 The e-beam world gun collector BPMs Isolated electrodes L-shaped pickup Reliable position measurement for all tree beams is challenging due to very different spectral content. Currently we can achieve ~100  m accuracy/resolution

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 18 Summary The e-beam quality in both TELs reached the level that made reproducible demonstration of beam-beam compensation possible. Generating dc e-beam does not appear very challenging, however generating pulsed beam (individual compensation of all bunches) does. Though the voltage itself is not a challenge – short rise time and high rep rate requirements make the development of the e-gun driver very challenging. The solid state Marx generator proved to be a reliable electron gun driver (with radiation shielding installed).

V. Kamerdzhiev for BBC teamTechnological aspects of Electron Lenses, errors and control 19 Plans Further reduce e-beam noise and ripple Simulate the effects of e-beam noise, ripple on beam lifetime and emittance growth (Lifetrac) Upgrade HV pulse generators (second generation Marx and solid-state modulator based on a summed pulse transformer scheme),  multi-bunch BBCompensation Install gaussian electron guns and perform head-on compensation studies (dc or pulsed) Study the effect of electron beam size on protons (lifetime, halo, Schottky) in both TELs Improve position measurement