electrostatic analysis of the gatling gun assembly

Gatling Gun External Review

Qiong Wu

on behalf of the Gatling gun design team 6/28/2012

Electrostatic Analysis of the Gatling Gun Assembly


Outline

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Assembly Parameters E-static study of the original model Modification and results Summary


The Assembly

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Models

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Parameter settings

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-250kV @ cathode shroud, water cooling tube, HV feedthrough

All other conducting surfaces are grounded Ceramic breaks and GaAs are set with corresponding

dielectric constant (ε) 2.8cm from the cathode

surface to the front surface of the anode 2.8cm


Analysis of the original design

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Potential

-62kV

-1.3kV

0.55MV/m

1.1MV/m

E field


high field regions

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Gatling Gun External Review 6/28/2012 8

Emax=14.3MV/m

10MV/m

12MV/m

9.5MV/m

8MV/m

13.6MV/m


E field in the vessel

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0.72MV/m 0.11MV/m

2.5MV/m @ the port edge

0.45MV/m

0.07MV/m 1MV/m @ the port edge


E field @ cathode

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13.6MV/m

11.4MV/m

E field along beam trajectory

Acceleration Deflection (~0.6% of acc.)


cathode shroud modification

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The cathode shroud edge has been changed to a more elongated elliptical curve.

version 3 version 2

version 1 (original)


Version 1: 13.6MV/m Version 2: 12.3MV/m Version 3: 12MV/m

11.7MV/m


Version 1 Version 2 Version 3

Version 1 Version 2 Version 3


Modification to other high field regions

6.9MV/m (org: 9.5MV/m)

6.2MV/m (org: 14.3MV/m)


Fill ceramic feedthrough with alumina + epoxy (εr=7)

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Emax @ 3.3MV/m (original: 10MV/m)

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Summary

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The goal of the Gatling gun assemble is to provide high current polarized electron beam @ above 200keV energy.

For our simulation of 250kV, the original design shows several ‘hot spots’ (>10MV/m) of electrostatic field region, and the most critical one would be on the cathode shroud surface.

Modifications have been applied to the design to lower the field level to below 10MV/m: Elongate the cathode shroud outer area Round corners of the vacuum chamber Retract the screw or change to ceramic screw Fill the ceramic corrugation with alumina + epoxy

The cathode shroud has a peak surface field of 12MV/m for 250kV acceleration, and will drop to ~10MV/m for 220kV

All other regions have electric field decreased to a safe level after modification


Thank you


Backup Slides


Electric field in x direction

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electrostatic analysis of the gatling gun assembly

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