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In recent experiments plasma electrons became trapped in a plasma wakefield accelerator (PWFA). The transverse size of these trapped electrons on a downstream diagnostic yields an upper limit measurement of transverse normalized emittance divided by peak current, eN,x/I. The lowest upper limit for eN,x/I measured in the experiment is 1.3⋅10−10 m/A.

Recent experiments at SLAC have shown that high gradient acceleration of electrons is achievable in meter scale plasmas. Results from these experiments show that the wakefield is sensitive to parameters in the electron beam which drives it. In the experiment the bunch lengths were varied systematically at constant charge. The effort to extract a measurement of the decelerating wake from the maximum energy loss of the electron beam is discussed.

Plasma production via field ionization occurs when an incoming particle beam is sufficiently dense that the electric field associated with the beam ionizes a neutral vapor or gas. Experiments conducted at the Stanford Linear Accelerator Center explore the threshold conditions necessary to induce field ionization by an electron beam in a neutral lithium vapor. By independently varying the transverse beam size, number of electrons per bunch, or bunch length, the radial component of the electric field is controlled to be above or below the threshold for field ionization. Additional experiments ionized neutral xenon and neutral nitric oxide by varying the incoming beam’s bunch length. A self-ionized plasma is an essential step for the viability of plasma-based accelerators for future high-energy experiments.

This paper describes an intercepting beam intensity profile and position monitor which was developed at SLAC. It has excellent spacial resolution as well as signal efficiency. The instrument utilizes the electromagnetic cascade shower emission effect. Net charge leakage signals comparable in magnitude to the intercepted beam current are easily obtainable. The latest model of the instrument is described. It consists of an array of closely spaced 0.0025 cm thick tungsten ribbons which are 2 r.1. long in beam direction. Experimental results as well as application of the basic idea to four different instruments are discussed. The instruments are: (1) a spectrum analyzer, (2) a vertical beam position monitor, (3) a ring inflection monitor for the SLAC electron-positron storage ring project, and (4) an accelerator beam phase space measurer.