Transcript Technical Issues to consider when making Wave/Particle

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
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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.
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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.
SWEAP / FIELDS Interface
SWEM (DPU)
SPAN-B
(electron)
DPU 1 / RFS
DPU 2 / TDS
FIELDS
SPAN-A
SPC
(Faraday Cup)
SWEAP
S/C DPU
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: SPANA-Ion, SPAN-A-Electron, SPAN-B-Electron.
• Both Electron and Ion scale micro-physics can be studied.
SPAN Intrisic Time Resolution
• Basic unit of time is the New York Second:
– 1 NYS = 1 sec * 2^17/150000 = .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= 0.853 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.
Wave/Particle Correlator tests
Ion Gun design
Ion Gun
Ionization
chamber
IF
V
G
VB
+Ions
-e
VS
• Ion Flux can be modulated by applying a varying
voltage (Vs) on the shield
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
0.1 Hz
1.0 Hz
10.0
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
200 Hz modulating ion flux
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
FFT of counts
Power
Frequency (Hz)
• Proper technique would be to use cross
wavelet correlation techniques. But… Easier
to bin by phase again.
Binning data by phase
V(phi)
?
CountRate(phi)
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:
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1 Full sweep
1 Targeted sweep
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
• End of presentation