1. Technical Issues to consider when making Wave/Particle Correlation Measurements
Davin Larson, Roberto Livi, Phyllis Whittlesey,
Keith Goetz, Stuart Bale,
D. Curtis, M. Ludlam, Amanda Slagle
Inspired by a desire to look for signs of local particle heating – or wave generation - that may be present in the near Solar region.
Generally Requires much better time resolution than any typical particle instrument can attain. (> 100 Hz)
Instrument add-on required a close collaboration between FIELDS and SWEAP. Developed after initial instrument selection (i.e. not proposed science – big payoff if it works!)
Technique is still in development.
All hardware/Firmware is minimal (and completed)
Software/ configuration / burst triggers still to be developed
System designed to be flexible enough to allow reconfiguration to test future wave-particle interaction theories.

2. SWEAP / FIELDS Interface
SWEM (DPU)
DPU 1 / RFS
SPAN-B (electron)
DPU 2 / TDS
FIELDS
SPAN-A
SPC
(Faraday Cup)
SWEAP
S/C DPU

3. FIELDS / SWEAP interface cable
Information exchanged in the F/S interface:
19.2 MHz clock signal (FIELDS 2  SWEM)
Provides single clock to operate both FIELDS and SWEAP instruments.
Measurements made simultaneously regardless of clock frequency drift.
Easier to filter out noise cross contamination.
Low latency communication packets (2-way)
Exchange: mag direction, burst status, operation mode
Particle Pulses (single channel - SWEM  FIELDS 2)
~200 ns long digital pulse sent to TDS directly from output of preamplifier/CFD (bypasses counters)
Time delays due only to cable length and a few FPGA gates.
Allows Wave/Particle correlations from up to 1 MHz
Potentially determine how energy is exchanged between E&M Fields and selected portions of the particle phase space density.
Particles Pulse can be selected from any combination of anodes from: SPAN-A-Ion, SPAN-A-Electron, SPAN-B-Electron.
Both Electron and Ion scale micro-physics can be studied.

4. SPAN Intrisic Time Resolution
Basic unit of time is the New York Second:
1 NYS = 1 sec * 2^17/ = .874 Seconds
Driven by FIELDS LVPS 150kHz requirement
4 distributions / NYS (0.218 sec resolution)
1 distribution = 256 accumulation steps
Time for single accumulation step= ms
(1172 Hz sampling frequency)
Sweep waveforms are table driven and reprogrammable.
Current table has:
32 Energy steps
8 Deflector steps
Sweep wave form can be held constant in time.

5. Wave/Particle Correlator tests Ion Gun design
Ionization
chamber
+Ions IF -e VG VB VS
Ion Flux can be modulated by applying a varying voltage (Vs) on the shield

6. SPAN – Ion Correlater tests
Sampling rate: 4.6 Hz (4 NYHz)
Modulating the Ion Gun flux at various rates by applying sinusoidal Vshield
Modulation: Hz Hz Hz

7. Wave/Particle correlater
Modulating Ion flux with 200 Hz signal.
Ions detected by SPAN-A-Ions
Particle pulses directed to SWEM and FIELDS-2
Vs waveform also delivered to TDS instrument.
Measured wave form (red)
Sampling at 2 Mhz
Mostly zero counts!
Binning at intrinsic SPAN time resolution

8. 200 Hz modulating ion flux

9. Wave/Particle correlater
Modulating Ion flux with 5 kHz signal.
Ions detected by SPAN-A-Ions
Particle pulses directed to SWEM and FIELDS-2
Vs waveform also delivered to TDS instrument.
Measured wave form (red)
Sampling at 2 MHz
Mostly zero counts!
Binning at intrinsic SPAN time resolution

10. FFT of counts
Power
Frequency (Hz)
Proper technique would be to use cross wavelet correlation techniques. But… Easier to bin by phase again.

11. Binning data by phase
V(phi) ?
CountRate(phi)

12. SPAN Intrisic time resolution (cont’d)
Targeted sweep mode:
SPAN alternates between a full sweep and targeted sweep
Targeted sweep based on which accumulation bin has the peak counts in the previous full sweep.
In 1 NYS:
1 Full sweep
1 Targeted sweep
Targeted sweep can be held at fixed energy and deflection angle.
All distributions can be accumulated over 2^N samples

13. End of presentation