All Seasons Cavity Analysis Results Alexey Kochemirovskiy The - - PowerPoint PPT Presentation

▶

Oct 11, 2023 307 likes •480 views

All Seasons Cavity Analysis Results Alexey Kochemirovskiy The University of Chicago/Fermilab Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014 Talk structure All Seasons Cavity (ASC) Breakdown physics

SLIDE 1

Alexey Kochemirovskiy The University of Chicago/Fermilab

All Seasons Cavity Analysis Results

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

SLIDE 2

Talk structure

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

All Seasons Cavity (ASC)
Breakdown physics
Dark current simulations and calculations
Results
Conclusion

SLIDE 3

All Seasons Cavity (ASC)

Was designed to be operated under various conditions Can the data provide us more info about BD?

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

SLIDE 4

ASC Geometry

Frequency = 810MHz Gap length = 15cm Radius = 14.5cm

Downstream end plate Upstream end plate Vacuum port Coupler

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

SLIDE 5

Breakdown pits

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

SLIDE 6

Breakdown pits distribution

Histogram of pit orientations

Can we explain that distribution? Can we deduce something from the pattern?

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

SLIDE 7

Fowler-Nordheim emission model

Work function

Describes electron emission from metal surface Surface field enhancement factor can be up to several hundreds Can be used to calculate the energy of electron beam

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

SLIDE 8

Magnetic field effect on breakdown

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

[ Effects of external magnetic fields on the operation of high-gradient accelerating structures. Diktys Stratakis , JuanC.Gallardo, Robert B.Palmer ]

SLIDE 9

Electron motion inside the cavity

Longitudinal motion

Relativistic correction

Bx, By consist of:

External B field
Bθ RF component
Br component from magnet

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

SLIDE 10

Simulation: model parameters

ACE3P simulation package
Bz = 3 Tesla
Field enhancement factor range

[140, 180]

Constant 20MV/m field gradient
Electron trajectories between

upstream and downstream end plate

Introducing “cavity

misalignment” Bx , By > 0

Checking both tilted and not-

tilted scenarios

Tilted upstream endplate Angle of tilt ~ 1.5o

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

SLIDE 11

Simulation results: example

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

β = 140 Bz = 3T Bx = 0.03T By = 0.03T Angle, degrees

Histogram of electron trajectory orientations

SLIDE 12

Calculation model

System of differential equations for electron motion

inside the cavity

RF fields are approximated by pillbox field solutions
Complex E(z) dependence is taken into account
External magnetic fields: Bz = 3T, Bx, By misalignment
Field map from MTA magnet

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

SLIDE 13

Preferable angle correlation with misalignment

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

Results

SLIDE 14

Conclusion

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014

Analysis is on-going
Model calculating trajectory of a single electron is

implemented

Dark current simulation analysis procedure is developed
Results confirm the hypothesis that cavity misalignment in

external magnetic field might cause certain pit orientation

Has a potential to be diagnostics technique
The tools developed for ASC effort is relevant for future

Modular Cavity data analysis of breakdown damage data.

Submitted abstract for IPAC’15

SLIDE 15

Alexey Kochemirovskiy MAP 2014 Winter Meeting, Dec 06, 2014