Presentacin de PowerPoint

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LTP diagnostics
Alberto Lobo ICE-CSIC IEEC
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Why is diagnostics analysis needed in the LTP?
LISAs top level sensitivity requirement is
LISA
This is so very demanding a previous LPF
mission is planned, with a relaxed sensitivity
requirement
LPF
Even if LTP works to top perfection, a
fundamental queston remains How do we make it to
LISAs sensitivity?
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DDS Data Management Diagnostics Subsystem

• Diagnostics items
• Purpose
• Noise split up
• Sensors for
• Temperature
• Magnetic fields
• Charged particles
• Calibration
• Heaters
• Induction coils

• DMU
• Purpose
• LTP computer
• Hardware
• Power Distribution Unit (PDU)
• Data Acquisition Unit (DAU)
• Data Processing Unit (DPU)
• Software
• Boot SW
• Application SW
• Diagnostics items
• Phase-meter
• Interfaces

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Diagnostics items use

• The methodology
• Split up total noise readout into parts e.g.,
  thermal, magnetic,...
• Identify origin of excess noise of each kind
• Orient future research in appropriate direction
  for improvement

1. Sensitive diagnostics hardware needs to be
designed and built
2. a) Suitable places for monitoring must be
identified. b) Algorithms for information
extraction need to be set up.
3. Creative research activity thereafter...
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Noise reduction philosophy
Problem to assess the contribution of a given
perturbation to the total noise force.
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Thermal and sensor requirements
Global LTP stability requirement 10-4 K/ÖHz ,
1 mHz lt f lt 30 mHz
Sensor sensitivity requirement 10-5 K/ÖHz ,
1 mHz lt f lt 30 mHz
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DMU test campaign
Transfer function
Thermal damper
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DMU test campaign
DMU EQM
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DMU test campaign
Open thermal damper, wiring and DMU
Insulating anechoic chamber for the test
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DMU test campaign
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DMU test campaign
Test general schematics
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DMU test campaign
Example run
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DMU test campaign
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DMU test campaign
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Thermal sensing summary

• Fully compliant with requirements
• Thermal gradients slightly distort performance
  at low frequency
• Magnetic properties of NTCs not an issue
• Research ongoing for improvements for LISA,
  encouraging
• first results

Refer to poster presentation by Pep Sanjuan, no.
27 and yesterday presentation
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Heaters
Heaters will be used to measure thermal
feedthroughs
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Heaters
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Heaters
Measurements Temperatures T5, T6 in IS1, T11,
T12 in IS2 Laser
Metrology x1 for IS1, x2 x1 D for IS2
Thermal signals temperature closest to
activated heater
Data Analysis fit data to ARMA(2,1)

• Should be OK in MBW even beyond!, and for
  each OW
• Can easily be improved, if necessary, at lower
  frequencies

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Heaters
Refer to poster presentation by Miquel Nofrarias,
no. 38
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Magnetic disturbances in the LTP

• Main problem is magnetic noise. This is due to
  various causes
• Random fluctuations of magnetic field and its
  gradient
• DC values of magnetic field and its gradient
• Remnant magnetic moment of TM and its
  fluctuations
• Residual high frequency magnetic fields

Test masses are a AuPt alloy 70 Au
30 Pt of low susceptibility
a 46 mm m 1,96 kg
and low remnant magnetic moment
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Quantification of magnetic effects
If a magnetic field B acts on a small volume d3x
with remnant magnetisation M, and susceptibility
c, the force on this small volume is
Total force requires integration over TM volume,
or
Most salient feature is non-linearity of force
dependence on B.
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Summary of magnetic requirements
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Magnetic sensor requirements
Req 2 A minimum 4 magnetometers. Req 2-1
Resolution of 10 nT/sqrt(Hz) within MBW. Req 2-2
Two magnetometers located along x-axis, each
as close as possible to the
centre of one of the TM, not
farther than 120 mm. Req 2-3 The other two may
be offset from the x-axis by an
amount not larger than 120 mm (TBC), their x
coordinate should fall between
the IS's at distances TBC. Req 2-4 Operation
of magnetometers compatible with full science
performance. Req 2-5 Final exact
choice of magnetometer locations depends on
final configuration of magnetic
sources. Limited adjustment of
magnetometer positions to within /- 10 cm along
x, y and z must be allowed until
system CDR.
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Magnetometer layout

• Magnetometers type
• 4 Flux-gate, 3-axis
• magnetometers
• Model is TFM100G2 from
• Billingsley Magnetics.

Areas for magnetometer accommodation
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Magnetometers accommodation
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Magnetic field map
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Magnetic field reconstruction

• Exact reconstruction not possible with 4
  magnetometers and
• around 50 dipole sources (solar panel)
• Tentative approaches attempted so far
• Linear interpolation
• Weighted interpolation various schemes
• Statistical simulation (equivalent sources)
• Best possible Multipole field structure
  estimation
• Only feasible up to quadrupole approximation,
  though,
• given only four magnetometers in LCA.

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Multipole reconstruction theory
In vacuum,
A multipole expansion of B follows that
corresponding to y(x)
The coefficients alm(r) depend on the
magnetisation M(x). In an obvious notation,
structure is
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Multipole reconstruction theory

• Evaluation of multipole terms is based on some
  assumptions
• Magnetisation is due to magnetic dipoles only
• Such dipoles are outside the LCA.

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Multipole reconstruction theory
Idea is now to fit measured field values to a
limited multipole expansion model. Arithmetic
sets such limit to quadrupole
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Multipole reconstruction theory
Arithmetics of reconstruction algorithm Data
channels 12 Mlm dipole 3 Mlm
quadrupole 5 Mlm octupole 7
these 3 are uniform field components
35 8 lt 12 gt some redundancy, OK
357 15, 3 unknowns too many!

• Summing up
• Full multipole structure up to quadrupole level.
• This is poor, only first order polynomial
  approximation
• Errors large --easily 100, and rather
  unpredictable
• Order of magnitude should be OK

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Multipole reconstruction theory

• Ways to improve magnetic diagnostics accuracy
• Fluxgates are
• Only 4
• Far from TMs
• Large size long sensor heads, 2 cm

We have recently started preliminary
activites at IEEC to assess feasibility of using
AMRs as an alternative to fluxgates. This kind
of research is intended for LISA.
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Magnetometers tests
m-metal enclosure
Billingsley TFM
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Magnetometers tests
LTP req.
Billingsley TFM
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Magnetometers comparative
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SQUID test of AMR device
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Magnetic diagnostics summary

• Fluxgate magnetometers are extremely sensitive
• Sensor core is large gt space resolution limits
• Sensor core is permalloy gt distance to TM
  constraints
• Box is large and somewhat heavy gt few sampling
  positions
• AMRs indicate good sensitivity
• They are very tiny
• Weakly magnetic due to small mass
• More thorough investigation needed underway at
  IEEC

Refer to poster presentation by Nacho Mateos, no.
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Control coils
Philosophy to apply controlled periodic magnetic
fields
Force comes then a two frequencies
Coils must be long (2400 turns), to maintain
reduced heat dissipation (few mW).
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Control coils

• Purpose
• To measure c in flight
• To measure M in flight
• To drive magnetic noise

Coils must comply with suitable reqs. of power
and stability. Workings with DMU have been
successfully tested and reported.
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General LTP layout
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Radiation Monitor

• Ionising particles will hit the LTP, causing
  spurious signals in the IS.
• These are mostly protons (90), but there are
  also He ions (8)
• and heavier nuclei (2).
• Charging rates vary depending on whether
• Galactic Cosmic Rays (GCR), or
• Solar Energetic Particles (SEP)
• hit the detector, as they present different
  energy spectra.
• This has been shown by extensive simulation work
  at ICL.
• Therefore a Radiation Monitor should provide the
  ability to distinguish
• GCR from SEP events.
• This means RM needs to determine energies of
  detected particles.

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Radiation Monitor
ICL simulations, based on GEANT-4. (Peter Wass
and Henrique Araujo)
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Radiation Monitor

• It is a particle counter with some
• specific capabilities
• It counts particle hits
• Retrieves spectral information
• (coincident counts)
• Can (statistically) tell GCR
• from SEP events
• Electronics is space qualified

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RM accommoation in S/C
Sun
Earth
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In place for test at PSI, Nov-2005
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In place for test at PSI, Nov-2005
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Radiation Monitor data
Radiation Monitor data are formatted in a
histogram-like form. A histogram is generated and
sent (to OBC) every 614.4 sec.
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Summary

• Thermal diagnostics
• Sensors fully in place
• Heaters in place, and integrating in EMP
• Improved sensitivity towards LISA in progress
• Magnetic diagnostics
• Sensors fully in place, sub-optimum expected
  performance
• Research in progress towards LISA
• Coils fully in place, working on EMP
• Radiation Monitor
• EQM built, green light to FM, PSI tests coming
  up
• More on RM in Tims talk

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End of Presentation