Latest Results on Cavity Gradient and Input RF Stability at FLASH/TTF Facility

TL;DR

This paper reports recent experimental results on RF stability and gradient control in the FLASH accelerator, providing insights relevant for the development of the ILC, with detailed analysis of pulse-to-pulse variations and a new gradient variation model.

Contribution

It presents new measurements of RF and gradient stability at FLASH and introduces a model for gradient variation during beam off conditions.

Findings

Stable RF and gradient performance observed during experiments.

Pulse-to-pulse variations quantified for beam on and off cases.

A new model describing gradient variation in beam off state is proposed.

Abstract

The FLASH L-band (1.3 GHz) superconducting accelerator facility at DESY has a Low Level RF (LLRF) system that is similar to that envisioned for ILC. This system has extensive monitoring capability and was used to gather performance data relevant to ILC. Recently, waveform data were recorded with both beam on and off for three, 8-cavity cryomodules to evaluate the input RF and cavity gradient stability and study the rf overhead required to achieve constant gradient during the 800\mu\s pulses. In this paper, we present the recent experimental results and discuss the pulse-to-pulse input rf and cavity gradient stability for both the beam on and off cases. In addition, a model of the gradient variation observed in the beam off case will be described.