Experiencing MPOD and Module HV Testing

By Thomas Pak (Fairfax, VA, USA)

Straw Workgroup Meeting Date: December 12th, 2012Location: CERN 6-2-024CERN Supervisor: Hans DanielssonInstitute Supervisor: Phil Rubin

What is MPOD?• HV/LV Power Supply Module with network

connectivity, controllability, and programmability• Using SNMP for Network Protocol for

communication and TCP/IP web access support

What is MPOD for Straw Module?•Provides HV power to straws – cover by

cover or by number of covers - and LV power to readout boards

•Enables users to monitor the status of the straw modules via MPOD’s supported network protocols

•Enable users to program the power supply’s behavior (such as maximum current and voltage, and scheduled behaviors)

Various Control Methods & Software

•Web access (TCP/IP, SNMP,Read-only)•MUSEcontrol (via USB connection,

Windows)•Labview Controls (TCP/IP, SNMP)•OPC Server (SNMP,TCP/IP, CAN-bus)

Industry standard, as well as CERN standard•Software Development(C++ library

accessible)

Pros and Cons on Each Method

• Web access▫ Read-only, low current resolution(μA)▫ Can be monitored even through mobile devices

• MUSEcontrol ▫ Full control Access, cannot be used to Remote Control

• Labview Controls▫ Doesn’t work well, low current resolution(μA)

• OPC Server▫ Overkill for small systems, high current resolution(nA)▫ Scriptable & widely supported▫ Free browsers available, but moderate to poor quality▫ Hard to see the readings, In-dept development in PVSS needed

• Software Development(C++ library accessible,SNMP) ▫ Can be developed in-house, low current resolution(μA)▫ Fully Controllable

OPC Server & PVSS

TCP/IP, SNMP

OPC Server

PVSS

ethernet

users

Straw Module

In-House Software Development

TCP/IP, SNMP

Windows/Visual Studio 2008

ethernet

users

Straw Module

In-House Software Development

LV Channels

HV ISEG Module Channels

Channel ON

Module HV Testing

• 2nd stage of HV test, following by 1st web-only HV test and followed by 3rd stage HV module noise-test

• The primary goal is to make sure there’s no current leakage

HV Testing ProcessStage 1: Web-only HV Test

Clean HV capacitorsCheck for current leakage

Check for noise-level

Stage 2: Module HV TestCheck for current leakage

Train the Straws under HV pressure

Stage 3: Module HV Noise TestCheck for Noise Level

Straws Behavior under HV

• Each straw acts like an 18nF capacitor• Under “normal” ambient conditions, it takes about

123 seconds to fully charge up. (2.3kV & 330nA current limit)

• Initial charging time varies widely between each straw. ( It could be anything 2 minutes ~ 48 hours)

• Once a straw gets “trained fully” under HV, all straws have a unique rise-time of about ~123 sec.

• 2 groups of current leakage behavior▫ 1~2nA : Does not recurr, when tested again▫ 20~25nA: Happens every time, but can be

eliminated, when HV lowered to 1.9kV ~ 2.0kV

Why do straws need HV training?

• (Speculation 1) Solid States Problem▫ There are always crystal structure defects, even on

the highest quality ultrasonic coating.

- -- - -

Electrons trapped in potential gradients due to defects in crystalline structure?

Cu & Au Coating Surface BEFORE HV Training

Cu & Au Coating Surface AFTER HV Training

Why do straws need HV training?

• (Speculation 1) Moist inside the Straws▫ which under HV would dry up and inhibit leakage

• (Speculation 3) Current Leakage to the module chassis▫ Not very likely.

Acknowledgement• Thank you all, straw team members, for your

generous support. I’ve learned so many invaluable lessons.

• This has been one of the best times in my life with learning experiences that would last for long time.