# Presentation: 354828

## BNL-SNS Diagnostic Status UpdateBCM System

- Martin Kesselman
- 2-5/6-04

## Outline

- Key Issues Addressed and Solved
- Status and Goals
- Failure Discussion
- Hand-off / Acceptance Criteria
- Remaining Efforts and Cost Estimate
- Summary

## On Schedule

## Key Design Issues Addressed & Solved

- Reference Document:
- BNL-SNS Technote 104 “Considerations for the Design of the Beam Current Monitor System for the Spallation Neutron Source (SNS)”, March 5, 2002
- _[http://server.c-ad.](http://server.c-ad.bnl.gov/esfd/bnlsns/104.pdf)__[bnl](http://server.c-ad.bnl.gov/esfd/bnlsns/104.pdf)__[.](http://server.c-ad.bnl.gov/esfd/bnlsns/104.pdf)__[gov](http://server.c-ad.bnl.gov/esfd/bnlsns/104.pdf)__[/](http://server.c-ad.bnl.gov/esfd/bnlsns/104.pdf)__[esfd](http://server.c-ad.bnl.gov/esfd/bnlsns/104.pdf)__[/](http://server.c-ad.bnl.gov/esfd/bnlsns/104.pdf)__[bnlsns](http://server.c-ad.bnl.gov/esfd/bnlsns/104.pdf)__[/104.](http://server.c-ad.bnl.gov/esfd/bnlsns/104.pdf)__[pdf](http://server.c-ad.bnl.gov/esfd/bnlsns/104.pdf)_
**Measurement of chopper characteristics vs. Ring turn by turn current.**
**DC restoration and droop compensation**
**Integration accuracy vs. sampling rate**

- Addressed by Aquiris

## Key Design Issues Addressed & Solved

- Goal of a single design to minimize design cost, and provide interchangeability
- Large dynamic range in Ring and RTBT
- RING/RTBT system designed to handle 50V peak input.
- We now use the protected amplifier for the MEBT/Linac/HEBT also
- Noise, Response characteristics, filtering and digitizing aliasing
- Testing
- Calibration

- Not Addressed by Aquiris

## Status and Goals

**Prototype(s) shipped to LBNL/ORNL**
**No Failures at Berkeley**
**Deliveries date back to Feb 2002**
**Total of 6 channels were delivered to ORNL (3 BCM electronic assemblies)**
- 1 MEBT (2 channels)
- Repaired twice
- 1 Linac DTL (2 channels)
- One channel reported failed (9/’03); received 12-16-03
- 1 Spare (2 channels)
- LANL PCI Interface would not run with updated operating system
**Unknown causes for failure still remain unknown**
**Extensive testing as soon as failures appeared**
**Internal BNL meeting was held to bring others into the effort to resolve the failure problem.**
- 15 people attended
- Details to follow in later slides

## Status and Goals

**Status:**
**All HEBT Current transformers were delivered to ORNL last June**
**All RTBT Current Transformers are in-house, tested, and awaiting assembly into the beam pipe hardware **
**Ring Current Transformer is on-order awaiting delivery (expected mid January) for assembly into Beam-Pipe hardware **
**Production (rev-D) BCM AFE boards are in-house**
** ****All components are in-house awaiting stuffing “go-ahead”**
**Computer order is in-place (part of an order of 100 PCs FY’03)**
**Awaiting release authorization & undergoing final specs revision**
**Goals:**
**Hardware in Spring**

## Failures –Timeline

- 1-7-03 Failure of MEBT unit reported
- Unit received 1-9-03 (s/n 0).
**Clear input signal failure mechanism noted (never repeated failure mechanism)**
- All resistors directly connected to input failed, including a 1 Watt resistor
- Amplifiers following these components also failed
- Unit repaired and returned 1-14-03
- One channel of this unit failed sometime later and was replaced on 8-14-03 (s/n 4)
- 4-23-03 Shipped 1 unit
- 7-24-03 Shipped 1 unit
- 8-12-03 ORNL tests units and describes a problem with one channel on each unit
- 8-14-03 Arrived at ORNL and found s/n 5,6 had in-operable PCI cards (not previously reported)– no further testing could be done
- 8-18-03 New board in MEBT (s/n 4) reported failed

## Failures –Timeline

- 8-25-03
- Received three units back with failed cards (s/n 4,5,6).
**Inconsistent failures on the three boards.**
- PCI board failed as-well on two of the systems, with catastrophic chip failure in each case, suggesting power supply problem.
- An input resistor had disappeared in one channel of one card
- The Analog Devices AD602 amplifiers appeared to have failed in all cases.
- A filter capacitor (47uF 16WV) on the +12 volt input line exploded.
- 10-3-03 Shipped two repaired systems (s/n 5,6) with sacrificial/protective components added.

## Rev-C Partial SchematicFailures - Dec 2003

## Failures – most recent

- 12-12-03 unit shipped back (to BNL) AFE s/n#5 (received 12-17-03)
- Initial data supplied by ORNL (12-15-03) indicated one channel stuck at rail (8192 counts).  Second channel producing strange output wave shape with very low amplitude (350 counts) and large offset (1000 counts).
- Unit initially repeated the display provided by ORNL.
- Calibrator outputs checked for appropriate amplitude level, and timing.
- Both channels were operating properly.
**We rule out any failures of the calibrator for both channels.**
- Failures observed in different places on the two channels
- Channel 1- small output, peculiar base-line ramping
- WBbuffer failure (Analog Devices (AD) U3A)
- amp Texas Instruments (TI) U3C (U3B not used) “peculiar distorted failure”
- AD (U2B) failure – large DC offset (attenuated from input signal)
- TI (U4A) suspected failed, although it had about correct output value (amp was disabled, not intended to be disabled)

## Failures –most recent

- 12-12-03 unit shipped back AFE s/n#5 (received 12-17-03)
- Failures observed in different places on the two channels
- Channel 2- Pinned at rail
- TI WBbuffer working properly
- AD (U202A) failed – no signal observable
- TI (U203C) appears OK
- TI (U204A) appears failed Pinned at 2.14V (amp was disabled, not intended to be disabled).
- AD (U202B) appears bad too, DC level was 0.584V
**One protection component (a dual diode – cathode to ground) failed on channel 2 at input to U202B**
***No  other sacrificial components failed on the power lines, or at amplifier inputs.***

## ORNL Questions Datel Power Supply

**Checked extensively**
**DATEL Power Supply Tests**
- Varied Input Voltage
- Varied over range 9 to 18 volts
- Applied power by abruptly applying voltage and slowly applying voltage
- Shorted output tests performed
- Unit limited output properly
- Open output Tests
- With one supply opened and the Input Voltage varied, achieved a maximum of 5.8 Volts (unbalance exceeded spec. of 20% minimum load).
- With a minimum drain of 200ma on one supply, achieved proper output levels on the other supply with varied input voltages.
- Unable to cause DATEL Failure within Specified Supply voltage range (raised input to as much as 20V with no apparent problems)
**Passed by Internal Review**

## Circuit Protection Added Prior to Dec 2003

**No direct indication of failure mechanism observed**
**Took approach to include expendable/sacrificial protection to help examine future failure paths, as-well-as add additional protection to amplifier inputs.**
- Input ports filtered by input capacitors to minimize RF pick-up.
- Added back-to-back diodes to all input amplifiers that had little isolation from input port to guard against excessive input voltages
- Added 12 Volt Transorb to 12 volt input power line
- Increased rating of 12 volt filter capacitor from 16WV to 25WV
- Added Zener clamping diodes to power supply output lines to help “crow-bar” the voltage levels to assure they do not exceed 5.6 volts (5V lines) and 3.6 volts (3V line) in an effort to protect amplifiers during transients and mark failure path.  These were “hand-picked” to assure proper voltage clamping.  The normal operating voltage is slightly below 5.0 volts due to current drain and finite inductor resistance in the filtering circuitry.

## Other Efforts to Resolve Failures - 1

- Installation of instruments at BNL-AGS & Other Locations
- Introduce a more “hostile” environment for the units in an effort to induce failures while maintaining tight control over the equipment.
- Unit has been installed at BNL “A-10” bldg
- Intend to install a unit in bldg 930
- Pursue manufacturer failure analysis of some failed ICs
- Effort to determine the path taken of destructive currents
- ICs have been shipped to both Texas Instruments (OPA3680) and Analog Devices (AD600) 1-22-04.

## Other Efforts to Resolve Failures - 2

- Continue to supply ORNL with units to get additional failure information.
- Outfit a unit with linear +/- 5V supplies to further rule out problems with the Datel supply.
- Internal BNL Review meeting convened
- 15 attendees - among them our best people
- No obvious design error observed
- Independent circuit analysis is being performed by an independent individual with an eye toward failure mechanisms.
- Recommendation to “make no changes until the failure mechanism has been identified”
- Instrument units and ship to ORNL for more failure testing/information
- Provide manpower support both at BNL and ORNL if necessary
- Beads on lines – recommended
- RF stimulation and sensitivity measurements – 5 Watt 400MHz Walkie-Talkie used to stimulate input and on open chassis
- Additional/continued investigations into failure mechanisms to be performed by BNL-SNS staff.
- Continued review of circuit design to be performed by BNL-SNS staff

## CALIBRATION

**PCI interface designed to operate and control the calibrator**
**Digital schematic complete**
**Digital calibrator art work in process**
**Analog high power prototype tested**
**Analog schematic in process**

## Hand-off and Plans

**Hand-off:**
- First article tested at BNL and witnessed by ORNL
- Additional units will show they meet specifications via their traveler documentation
**Plans:**
**Now to May;**
- Test in Lab
- Test in BNL bldg A10
- Test in BNL bldg 930
- Test at ORNL
- Supply two units immediately  (February 2004)
- During DTL commissioning operate together with FBCM
**Early May;**
**Make a decision as to how to proceed**
- Use Aquiris?
- Execute a fix?

## Remaining Efforts - 1

- Low Current Calibrator/Driver
- Complete PC board artwork for rev-1
- Manufacture boards & stuff
- Test
- High Current Calibrator
- Complete PC board artwork for rev-1
- Purchase components
- Manufacture boards & stuff with components
- Test

## Remaining Efforts - 2

- Stuff BCM electronics circuit boards
- Prepare all PC chassis with software & mounting components required for interface with AFE
- Install all electronics circuit boards
- Test system
- Check all amplifier gains and document
- Calibrate calibrators and document
- Check all software & document
- Prepare shipping memos with detailed data and Ship

## Remaining Cost Estimate (25 units)

## Summary

**Ready to go into production of BCM electronics**
**Beam-pipe components ready for transformers**
**Failure mechanism path indication provided by expendable Zener diodes on supplies and protection diodes on amplifier inputs**
**Continued testing at BNL & ORNL**
**Failures at ORNL still unexplained**
**Estimated Costs to complete 25 Units (50 Channels):**
**Add’l Purchased parts and labor****	****$72,125**
**Engineering Labor****	****	****	****1000 Hrs.**

## Back-up material

## SNS DESIGN PARAMETERS

- Energy................................1 GeV
- Intensity.............................. 1.5 x 1014 protons
- Repetition Rate.......................60 Hz
- Number of Bunches.................  1
- Injection duration...................  1.0 msec
- Revolution Period.................... 945 nsec
- Bunch Length......................... 645 nsec
- Number of turns...................... 1060

## BCM Requirements

**From SNS Diagnostics AP Requirements (03/01)**
- MEBT to HEBT 0.3 - 1000 us,
- 15 to 52mA
- Accuracy < 1% of FSR
- Resolution 0.1% of FSR
- Detail within mini-pulse- available on demand
- Ring to RTBT 5e10 to 2e14 Protons
- 0.015A to 100A
- Accuracy < 1% of FSR
- Resolution 0.1% of FSR (relaxed to 0.5% for gain steps compromise)
- Turn-by-turn data- available on demand

- Interpretation of requirements

## 1st Unit Returned 1-9-03s/n 0 - Channel 2 was OK

## Comments – s/n 0 - 1st Unit (1-9-03)

- Channel 2 was OK
- Three resistors connected to the input port failed
- R6 opened (discolored – 1Meg)
- R33 opened (discolored)
- R34 opened (visible crack) 120 Ohm 1W
- Amplifiers fed by these resistors failed
- U3A (OPA3680) had a large DC (+3V) on pin 2 (+ input to wide-band buffer)
- U2A (AD602) had a large DC at output (-3.8V)
- Remaining amplifiers in the gain chain may/may-not have been OK.  They provided outputs that reflect the bad offsets due to earlier (in the chain) failures.

## Units Returned 8-25-03s/n 4,5,6

## Comments – Failures s/n 4,5,6 (8-25-03)

- When amplifiers failed Datel supply was loaded down
- AD602  seems to fail in such a way as to develop a large DC on the control input terminals.
- Input resistor for s/n 6 to AD602 was missing from the board.
- Exploaded +12V input supply filter capacitor replaced with 47uF 25WV.

## Failures s/n 5 (12-17-03)

## Acceptance Matrix 10-Apr-2001 per Dan Stout

## Diagnostics Hand-off  General PhilosophyPresented Nov 29, 2001

- Assembly and Test for all systems will be accomplished at BNL (exception is BLM?)
- Funding for documentation has been removed from BNL budget. ORNL will be responsible with documentation. Agreement with ORNL is that they will provide system specialists one manweek/month at BNL starting ASAP.
- ORNL will be responsible for Installation, System Integration, Documentation, Commissioning (requires early ID of BNL support requirements)
**Acceptance criteria:  The delivered components must meet  the requirements of the final design review.**

## BNL Diagnostics by System Presented Nov 29, 2001

- 1.5.7.1  BPM
- HEBT, Ring, and RTBT PUE’s - delivered to Vacuum Group
- Ring and RTBT Electronics - all assembly and test at BNL
- 1.5.7.2  IPM - Ring only, all assembly and test at BNL
- 1.5.7.3  BLM - BNL responsible project wide. Test 5-10% at BNL by BNL, remainder at ORNL by ORNL
**1.5.7.4  BCM - BNL responsible project wide, all assembly and test at BNL**
- 1.5.7.5  Tune - Ring only, all assembly and test at BNL
- 1.5.7.6
- Carbon Wire - by LANL
- Laser Wire - proliferation remains to be determined, all assembly and test at BNL
- 1.5.7.7  BIG - Ring only, all assembly and test at BNL
- 1.5.7.8 Video Foil - Injection area only, all assembly and test at BNL