AVSAP Autonomous Voltage Spike Analysis Program Said Rahimzadeh – Kalaleh Engineering Physics

Thank You Fermilab – TD (Magnet Systems Dept.) Michael Tartaglia Conor Donnelly SIST –Elliot McCrory Equal Opportunity Office –Dianne Engram Jamieson Olsen

Outline Background on Superconductivity (SC) and SC accelerator magnets Voltage Spike Studies at FNAL –Present Voltage Spike Detection System (VSDS) –Need for Automation AVSAP –Data Acquisition (DAQ) –Data Processing –Post-Processing Features

Superconductivity 1.T < T c 2.B ext < B c 3.J < J c BCS Theory Electrons find it energetically favorable to form Cooper pairs ! Perfect Conductor !

Application: SC Accelerator Magnets Particle beams are bent and focused by high field SC magnets carrying high currents ( >10,000 amps !!!)

Nb 3 Sn Critical Surface T = T (B, J) B = B(T, J) J = J(T,B) Cold !!!

MO images of the flux distribution in a Nb 3 Sn film at 3.5 K for increasing magnetic field

How do we detect voltage spikes in SC magnets at Fermilab ?

HARDWARE Voltage Spike Detection System VSDS circuit block diagram Developed at Fermilab for the detection of small magnetic flux changes in superconducting magnets

Software Quench Data Analysis VSDS

VSDS Application

Why develop a new software ? To study these spikes, it would be good to have : Statistical analysis tools Spectrum analyzer User-defined Filtering (+SNR) Width of spikes (~Energy) VSDS requires the user to manually search file by file for V p, I avg, & all other desired values. Time consuming for the user (student) !!! ~ 3 hours to collect only V P and I avg for spikes of one ramp. Student TD

The Solution … Autonomous Voltage Spike Analysis Program

Functions.m Program Structure * Detection method: zero crossings in dv/dx (with thresholds)

Start ! Depending on the user’s needs, a single file or many files may be processed. –Each option will lead to a different GUI platform

Single File Processing The images in the following slides show the available features when processing a single file.

Fast Fourier Transform (FFT) Time Domain Frequency Domain Low-Pass Filter High Frequencies ( f > 15 kHz)

Inverse Fast Fourier Transform (IFFT) Frequency Domain Time Domain

Export to Excel

Multiple File Processing The images in the following slides show the available features when processing multiple files.

Spike Histogram as a function of amplitude (mV) Spike Histogram as a function of current (amps)

Data Handling Features Save any of the following plots (as JPEG) for every file processed : –Raw Voltage Signal –Filtered Voltage Signal –Spike Snapshots Save any of the following statistics (as JPEG): –2D I-V Profile –3D Spike Histogram; S (I,V) –Voltage Histogram –Current Histogram Export Data to MS Excel

Extended Common Features Band-Pass Filter Application Adjustable parameters for spike detection –Amplitude Threshold –Width Threshold

But how well does it work ? Lets compare results…

AVSAP v.s. Conor

Good results, but a few discrepancies with small amplitude spikes. Why ?

Hidden Spike ! Spikes Previously Obscured by the Noise are now detected. In all cases, AVSAP detected more spikes than a human, and these spikes were verified to hold true.

Concluding Remarks A software for automating the detection of voltage spikes in superconducting magnets has been developed. This software will remain at Fermilab for future studies of these thermo-magnetic instabilities in superconductors.

No more tedious file inspection for students to detect voltage spikes !

Thanks !