Synchroscan streak camera imaging at a 15-MeV photoinjector with emittance exchange

TL;DR

This paper describes the upgrade and application of a synchroscan streak camera system at Fermilab's photoinjector to achieve high-precision, synchronized measurements of laser pulses and electron beams, enabling detailed analysis of beam dynamics.

Contribution

The paper introduces a synchroscan module and phase-locked delay system for streak cameras, enhancing measurement precision and enabling simultaneous imaging of laser and electron beam diagnostics.

Findings

Achieved less than 1.5ps trigger jitter for streak camera measurements.

Successfully measured bunch-length and phase effects during emittance exchange.

Enabled simultaneous imaging of laser pulses, OTR, and diagnostics lasers.

Abstract

At the Fermilab A0 photoinjector facility, bunch-length measurements of the laser micropulse and the e-beam micropulse have been done in the past with a fast single-sweep module of the Hamamatsu C5680 streak camera with an intrinsic shot-to-shot trigger jitter of 10-20ps. We have upgraded the camera system with the synchroscan module tuned to 81.25MHz to provide synchronous summing capability with less than 1.5ps FWHM trigger jitter and a phase-locked delay box to provide phase stability of ~1ps over 10s of minutes. These steps allowed us to measure both the UV laser pulse train at 263nm and the e-beam via optical transition radiation (OTR). Due to the low electron beam energies and OTR signals, we typically summed over 50 micropulses with 0.25-1nC per micropulse. The phase-locked delay box allowed us to assess chromatic temporal effects and instigated another upgrade to an all-mirror input optics barrel. In addition, we added a slow sweep horizontal deflection plug-in unit to provide dual-sweep capability for the streak camera. We report on a series of measurements made during the commissioning of these upgrades including bunch-length and phase effects using the emittance exchange beamline and simultaneous imaging of a UV drive laser component, OTR, and the 800nm diagnostics laser.