TTF Dark Current Kicker and NML Simulations

C.Y. Tan

23 Jan 2007

Overview

A summary of what TTF has measured and plan to do

This comes from “Dunkelstrom Kicker TTF2”

Caveat: I don't speak German, so interpretation of slides should be taken with a grain of salt.

Simulations done with ASTRA for NML

Goal is to have some idea of the dark current energy distribution

Baseline for the dark current kicker.

Layout

kicker

collim

screen 3BC2?

16m

23m

23.3m

Energy of beam at kicker = 130MeV

35cm dispersion at screen

Not 50A but 25A! See Slide 15 of original paper

Simulations Started for NML

Create dark initial distribution using Fowler-Nordheim

Match the simulated current to that measured by Fliller et al., “Time Dependent Quantum Efficiency and Dark Current Measurements in an RF PhotoCathode Injector with a High Quantum Efficiency Cathode”, Fermilab-Conf-05-185-AD.

Calculate the energy distributions at the various points at NML.

See where particles are lost. Will kicked dark current cause a quench?

Calculate the efficiency of the kicker.

Layout

The Initial Distribution

, , A are free parameters to fit with observations. Assume dark current from cathode. See J.H. Han's thesis

Ez (MV/m)

Electron Distribution

Some Preliminary Results

Before CC1:

Lost 85% (1448/10000) of dark current before CC1!

Only 2% of main bunch

Before CC2:

Lost another 80% (257/10000) of dark current going through CC1!

0% lost in main bunch.

Compare with J.H. Han's Measurements

Conclusion

Work has started on NML dark current kicker.

Start initial design of kicker.

Get some engineering tolerances.

Cheng-Yang Tan

2007-01-22T11:03:33