All Seasons Cavity Analysis Waveform analysis Spark - - PowerPoint PPT Presentation

All Seasons Cavity Analysis

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Waveform analysis

Spark characterization

• A. Kochemirovskiy

Uchicago/Fermilab

Motivation

• IPAC paper submission deadline is:

Wednesday, 29 April, 2015 at midnight in Richmond (GMT-5) “Breakdown characterization in 805MHz pillbox-like cavity in strong magnetic fields”

• Physical questions we want answers to:

– What does typical spark look like? – How does it depend on pulse parameters?

• Run history questions I want answers to:

– Magnetic field – Any info there is

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Data

Labview’s Log files Scope’s .bin and .csv files Capture every 20 mins + “sparks” (not synced)

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MTA3 server

Relevant formula

CSV = SCV = CVS ≠ ASC

CSV - Comma Separated Values SCV - Space Construction Vehicle ( StarCraft 1) CVS - Consumer Value Stores ( Pharmacy )

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Waveforms collected

Lecroy - fastest scope ( 0.1ns sampling rate) Tektronix - “slow” scope ( ~ 1ns sampling rate)

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Data structure

Log Files Lecroy CSV Lecroy PNG B field 28-Feb

3T?

:

3T?

13-Mar

3T?

:

3T?

21-Mar

3T?

:

3T?

23-Mar

3T -> 0T

:

0T

:

0T

5-Apr

1T

6-Apr

2T

7-Apr

3T

8-Apr

3T

:

?

22-Oct

?

• ~ 2000 CSV files, ~ 25Gb
• Python – nice programming interface,

although weaker math libraries

• Looked at the pickup signal data only

(Lecroy Channel 1)

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Comments

Calibration

2013-03-02 11:38:34 Calibration point: 1.61 V pickup on LabView = 1.06 V on scope (with 6dB att) = 7.8 MV/m 2013-03-02 10:12:55 Calibration point: 1.02 V pickup on LabView = 0.74 V on scope (with 6dB att) = 5.5 MV/m

y = 7.4006x - 0.0094 R² = 0.9998 10 12 14 16 18 20 22 24 1.5 2 2.5 3 3.5 Gradient, MV/m Lecroy Max Pickup Amplitude, V 4/8/2015 7

Gradient [ MV/m] = 7.4* Max_amplitude

Run history

Based on Labview’s Probe Peak data Based on Lecroy waveforms

26 MV/m

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Gradient [ MV/m] = 7.4* Max_amplitude_scope (CSV) Gradient [MV/m] = 3.7* Probe_Peak ( Labview Log)

Pickup Signal

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Envelope

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Envelope of envelope

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Normal event

Max_amplitude

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Normal event

T – decay time

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τ – Decay constant

(decay time constant)

Typical spark

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Typical spark

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Decay times

March 11th-20th March 20th – 23rd March 23rd – 27th March 27th – April 10th

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Cutting

Decay constants vs gradient

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Normal events Sparks

March 13th – Apr 5th Apr 5th – 6th Apr 6th – 7th Apr 7th – 10th

Decay constants vs gradient – normal events

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March 13th – Apr 5th Apr 5th – 6th Apr 6th – 7th Apr 7th – 10th

Some spark statistics

Total number of sparks - 89

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Spark current estimation

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Basic model: all stored energy

𝐷𝑊2 2

goes into the spark current: 𝑅 = 𝑅0exp(-

𝑢 τ )

I = −

𝑅0 τ exp(- 𝑢 τ )

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Backup

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# 2013-03-23 16:18:58.191, 1354823, Comment, After ramping down the magenetic field, we

• baserve abrupt change in the tempearute reading (19 --> 7 -->16, etc)

2013-04-05 17:59:00.683, 2461790, Comment, Now at 1T. 2013-04-06 11:09:42.426, 2522471, Comment, Now at 2T 2013-04-07 11:01:42.137, 2606858, Comment, Now at 3T 2013-04-08 20:13:57.921, 2724031, Comment, Start ramping down B field. 2013-03-02 09:53:45.582, Comment, Running at 3T, good vacuum IG1=7E-9, current pickup amplitude 476mV (3.5 MV/m) 2013-03-02 10:12:55 Calibration point: 1.02 V pickup on LabView = 0.74 V on scope (with 6dB att) = 5.5 MV/m 2013-03-02 11:29:54.079, Comment, Calibration point: 1.4 V pickup on LabView = 0.95 V on scope (with 6dB att) = 7 MV/m 2013-03-02 11:38:34 Calibration point: 1.61 V pickup on LabView = 1.06 V on scope (with 6dB att) = 7.8 MV/m

Backup

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