ERL Differential Current System Status

Peter Cameronwith contributions from Michelle Wilinski and

Christophe DeFrance (Bergoz)

17 Sep 07

Outline1. Damage threshold estimate

2. Test setup pictures, block diagram,…

3. DSA measurementsa) Noise floor and DC drift

b) Effect of temperature

c) Conclusions from DSA measurements

4. FPGA measurements a) Block diagram

b) measurement sensitivity

5. Discussion, conclusions,…

1 uA-sec (6x1012 electrons, or 1uC) used in the following slides

signal generator

Bergoz Bergoz ElectronicsElectronics

Bergoz Bergoz ElectronicsElectronics

Agilent FFT box

FPGAboard

Floppy

ethernet

Excel

LabVIEW

Test Setup Block Diagram

scope

not 1/f !!!

Full span (PCT nominal BW is 10KHz) noise spectrum

No averaging

Comparison of single toroid and difference spectra

single toroid

difference of the two toroids

Bergoz – 5 averages (note log scale)

Comparison with Bergoz measurement

Include spectral shaping in null?

400Hz BW noise spectra

Bergoz – 5 averages (note log scale)

Effect of temperature stabilization

Out of office

What happened here???B field change?

100uA/gauss gives .02 gauss

.01667 uA-sec on 1 minute

~0.1 nA-sec driftover 160 minutes

Time/temperature dependence of difference current

.0033 uA-sec

Zoom on previous slide

Conclusions from DSA Measurements

1. Toroids meet Bergoz spec in uncontrolled conditions (temperature, magnetic field) of office test environment

2. Study and optimize proper thermal shielding 3. Frequent null calibration should not be needed4. Slow loss limit should be in the range of 1nA-sec

or better5. Should be a useful diagnostic

a) Machine protectionb) (unprecedented and essential) Halo studies at ~10-6

need moveable scrapers?

6. Need to understand vector averaging (more on this later)

Outline1. Damage threshold estimate

2. Test setup pictures, block diagram,…

3. DSA measurementsa) Noise floor and DC drift

b) Effect of temperature

c) Conclusions from DSA measurements

4. FPGA measurements a) Block diagram

b) measurement sensitivity

5. Discussion, conclusions,…

BPM (also FCT, DCCT, BLM,…) Block Diagram

signal generator

Bergoz Bergoz ElectronicsElectronics

Bergoz Bergoz ElectronicsElectronics

ML403

ethernet Lab VIEW

Test Setup Block Diagram

AtoD

FPGA wrapper

Simulink

Signal processing, feedback loop, MPS

interface,…

DIODAC

MPSnull

MPS function runs independent of Control System - robustness

BPM Module

Embedded processor running

vXworks/EPICS

9.38MHz RF reference

x4 or x8Laser pre-

trigger

Beam permit

Process Variables(beam position,…)

Process Variables(machine mode, beam mode,…)

FPGA

1 sec event

A/DPUE signals

FPGA board control panel

spectral content of simulated beam loss

Next slide is zoom on this

0 1 2 3 4 5 6 7 8 9 10 Time [minutes]

1 uA-sec loss signal

FPGA-based beam loss measurement (S/N ~same for DSA and FPGA)

no loss signal

Comments, conclusions• Consider toroid upgrades for RHIC

– Present DCCTs are 5uA/rtHz?– Going to 0.1uA/rtHz would give much more sensitive diagnostic for machine tuning -

this is important!

• Implementation of DI measurement on FPGA board was straightforward ~2 man-weeks of Joe Mead, 1 man-week of Pete Cameron

• Paradox? need to understand vector averaging,… see simulation• Where from here?

– Basic system functionality and spec demonstrated– I’m on travel for most of the coming month, then Run 8– Priority shift to BPM electronics

• BPM system– Libera demo box due in any day now (after 3 months of trying to get it)– I’m at ITech (Slovenia) next week to work out details of Libera in ERL– Commercial vendor (the major supplier of demo boards) exploring design and fab of

COTS FPGA board to our spec (~$1K vs ~$10K or more for Libera box, and much simpler)

– Joe Mead is fabbing 4ch fast digitizer mezzanine for ML403

Hold off on further DI development until next spring?

Suggestions for upcoming meeting agendas

• Sep 17th – presentation and discussion of DCCT and differential current status

• Sep 24th– presentation and discussion of Profile status • Oct 1st – presentation and discussion of BPM status • Oct 8th – Scrapers and collimators