RF System Requirements for the ILC Vertical Test Stand at IB1

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RF System Requirements for the ILC Vertical Test
Stand at IB1
J. Ozelis TD/Test Instrumentation Dept.
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• Motivation
• Support the goals of the ILC cavity performance
  development program - verify cavity processing
  improvements by quantifying cavity performance in
  a reliable, reproducible, and efficient manner.
• How do you quantify cavity performance ?
• Measure Q0 vs Temperature
• Measure Q0 vs E
• Measure Field Emission (radiation)
• Investigate effect of low temperature externally
  performed bakeout on Q-drop
• Baseline Design Tesla cell shape, 9 cells, 1.3
  GHz. Alternate geometries, cells,
  superstructures, may also be evaluated.

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• Basic Requirements for a Vertical Cavity Test
  System
• Provide stable RF power to the cavity, with
  control of amplitude, relative phase, and
  frequency
• Measure CW incident, reflected, and transmitted
  power of the cavity (including transmitted power
  from HOM couplers if so equipped)
• Measure radiation (g) produced from FE (field
  emission) or MP (multipacting)
• Measure cavity frequency, and test condition
  variables
• Provide interlocks for personnel
• Provide automated data acquisition and control
  (reproducibility)
• Calculate cavity performance parameters (E, Q0)
  from power measurements and field decay time
  constant

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• Cavity Specific Requirements
• Various properties of the ILC cavity and the
  manner in which testing is to be performed
  determine the specifications and requirements of
  the RF system.
• Some of these properties are
• Cavity geometry/support
• Cavity frequencies
• Cavity ultimate gradient and shunt impedance
• Field probe coupling
• Input probe coupling

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• Cavity Support and Frequency Considerations
• Cavities will not be mounted in a tuner or
  maintained at design resonant frequency (1300
  MHz). Cavity frequencies will vary as a result
  of
• chemical processing (degree, number of times)
• bench tuning
• manufacturing tolerances
• He bath temperature
• Lorentz force detuning
• Additionally, we will want to be able to excite
  the cavities in any of the 9 pass-bands.
• So how does this impact the system frequency
  range?

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Frequency Effects
Effect D f
Bench tuning/manuf tolerances 10 to 100 kHz
Chemical processing (20mm ) -200 kHz
Lorentz force detuning (_at_ 35-40 MV/m) -1 to 2 kHz
He bath temperature (4K ? 2K) 50 to 100 kHz
So far only a few 100kHz but biggest
consideration is cavity pass-band frequencies.
Typically, at 2K ? mode 1300.3 MHz ?/9 mode
1275.8 MHz So we see a spread of 25MHz between
modes. Therefore, the system should have a
frequency range of 1270-1305 MHz
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Cavity Gradient, Q0, L, and r/Q
These factors determine the incident power
required to drive the cavity as a function of
gradient and Q0. We have Ploss E2
L/(Q0(r/Q)) For an ILC cavity at Q0 5 x 109 and
35MV/m, this yields about 250W. Given that 2-3 dB
of attenuation is a reasonable and achievable
design goal for the high power distribution
system (cables, switches, connectors), this
implies a high power amplifier with an output of
500 W
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Cavity Coupling
The coupling of the fundamental power coupler
(FPC) and field probe (FP) to the cavity will
determine how much power goes into and comes out
of the cavity. Input Coupling If QFPC is such
that cavity is not near critical coupling, then
additional power is needed to reach design
gradients. Since we may have 300W (2.2dB loss in
dist. system), we need to keep the reflected
power below about 50W at maximum gradients. This
means that b should be less than 2.2. This means
that QFPC should be gt 2 x 109. In practice it
should be easy to reproducibly achieve QFPC 8 x
109 to 1 x 1010, even with a fixed coupler, as
antenna length is not difficult to control.
(Concurrent development of a variable coupler
mechanism will lead to greater control over b,
and the ability to keep b near 1.)
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Cavity Coupling
Field Probe Coupling The field probe coupling,
which is characterized by QFP, determines the
power coupled out from the cavity (for a given
gradient), which is then fed back into the PLL
for loop control and for measurements. This power
level changes over a wide range due to the range
in gradients we wish to measure and variations in
QFP, from cavity to cavity. The dynamic range
due to gradient spread is on order 104, while a
range of 15 in field probe coupling could yield a
total dynamic range of 106 ! An achievable level
of control over setting QFP can reduce this range
somewhat, to lt 105, a more reasonable value.
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With reasonable control over QFP, we can expect
transmitted power levels from a few tens of mW to
about 1W.
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Other Considerations

• Additional requirements are imposed on the RF and
  measurement system based upon ILC measurement
  needs and previous cavity testing experience
• Frequency measurement resolution (for Lorentz
  force detuning) lt 1 Hz
• RF pulsing (0.5-1 Hz, natural cavity rise time)
  for FE processing
• Low system drift (minutes)
• Measurement of radiation to quantify FE
• 360 phase control (manual and automated)
• Various signals available for viewing on
  oscilloscope (decay, coupling)
• Interfaces with interlocks/PSS
• Measurements and logging of test conditions
  (temp, pressure, LHe level)
• Control and measurements automated
• These requirements, coupled with those imposed by
  the characteristics of the cavity, probes, and
  performance envelope, serve to provide a baseline
  for the RF Measurement System specifications.

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System Specifications/Requirements Summary -
1 Frequency Manually adjustable (coarse fine
tuning) over the range 1.25-1.35 GHz Measure and
record frequency as part of DAQ
SW Resolution/sensitivity/stability lt
1Hz Phase Manual phase control Programmable
phase control, range 360, resolution
0.1 Automatic phase optimization routine in
SW Phase stability 1 drift over 10 minutes

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System Specifications/Requirements Summary -
2 Power Supply Measurement RF Power
supplied via 500W SS amplifier, 1270-1310MHz,
50dB gain min. Amplifier protected against
maximum reflected power Measurement of Pi, Pt,
Pr, and PHomA,B using calibrated power meters,
and also with crystal (diode) detectors (for time
dependent measurements or qualitative visual
observation) Variable attenuator ( 30dB) in
series w/ switchable 30dB gain amplifier to
regulate Pt input signal on crystal (diode)
detector, to maintain operation in the square-law
regime, and regulate loop gain RF system stable
and operable between E 0.1 40 MV/m RF Pulse
capability pulse width 100ms 5 sec, at rep
rates up to 10Hz Computer controlled amplitude
and phase adjustment via VM (vector modulator)
Amplitude resolution lt .2 dB (12 bits if typical
digital VM) Phase resolution lt 0.5 (12 bits if
typical digital VM)

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System Specifications/Requirements Summary -
3 Radiation / Interlocks Measurement and
logging of radiation inside dewar shield
enclosure by DAQ system. High power RF enable
interlocked w/ Personnel Safety System to be
designed/implemented/maintained by FNAL AD/ESH
Dept Interlocks Grp. Interlock system monitors
both external-to-dewar area monitor radiation
signals and dewar lid closure status, and
displays status.

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System Specifications/Requirements Summary -
4 Acquisition and Control SW Automatic Pt decay
measurement Automatic calculation of
b Interactive cable calibration
routine Continuous online display of E, Q0, Rad,
Pi, and Pr Online display of Pi, Pr, Pt, and
correction (calibration) factors RF output power
control Phase control Phase optimization
routine Display of cryogenic status (LHe level,
temps, dewar pressure(s)) On-demand calculation
of Q0, QFP, QFPC, Qext HOM1, Qext HOM2, Eacc and
all associated errors. Logging of all data to
ASCII file Graphic display of Q0 vs Eacc Graphic
display of Rad vs time, w/ Rad vs Eacc option

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Design of the RF System for the ILC Vertical Test
Stand at IB1
J. Ozelis Fermilab/TD/Test Instrumentation
Dept. T. Powers Jefferson Lab/AD/Engineering
Dept.
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• Design Choice Motivation
• Minimize development costs
• Minimize risk
• Maximize ease of operation
• Robust system for use in a production, not
  development, facility, usable by on-experts
• Tight schedule requirements

• So base it on the JLab VCO/PLL-based system
• Existing design that has tested gt 500 cavities,
  800 tests, in a production environment (CEBAF,
  SNS, ILC)
• Off-the-shelf components
• Existing SW for control, acquisition, and data
  analysis

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• System Functional Description
• The system is comprised of several integrated
  functional modules
• RF Source/VCO/PLL
• Transmitted Power Network
• Power Measurement
• High Power Amp/Switching Network
• Diode Detector interface/Buffer Amplifier
• Each module can be assembled, optimized, and
  tested separately.

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System Block Diagram - General
Loop Amp
Mixer
f shifter
Trans. Sig. Amp
LP Amp
RF Source
VM/I/Q
RF switch.
HP Amp
Cavity
PSS Intlk. - example
Power Measurement Module
Computer Interface
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System Block Diagram - General
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Source/PLL module
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Source/PLL module
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• Source/PLL module
• Classic VCO/PLL circuit w/ mixer, loop amplifier,
  RF source
• Mixer output provides FM signal for RF source
• Vector modulator provides phase/attenuation
  control
• RF source Agilent E4422B (10dBm output, 0.01Hz
  freq resolution, up to 20MHz FM range at 1.3GHz,
  output coupled to Agilent Model 531332A freq.
  ctr. via 10dB directional coupler)
• Mixer MITEQ DM005LA2
• Phase shifter (manual) Advanced Technical
  Materials model P1213 (180/GHz, 0.6dB IL, VSWR
  1.3)
• Vector Modulator GT Microwave M2D-32A-5HV (60dB
  atten. w/0.02dB res., 360 phase control w/ 0.1
  res., max 15dB IL
• Signal Amplifiers MiniCircuits ZX60-2522M (22dB
  gain)
• Output AM w/ GaAs FET switch MiniCircuits
  ZASWA-2-50DR (1.8dB IL, gt 80dB isolation)
• Output switch (interlocked) Narda SEM123D,
  SPDT, failsafe, TTL, 0.2dB IL, 80dB isolation

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Transmitted Power Network
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Transmitted Power Network
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• Transmitted Power Network
• This module conditions and amplifies the
  transmitted power signal from cavity under test.
  Provides input to mixer, and signal for power
  measurements. It must accommodate a wide (105)
  dynamic range.
• Attenuator Hittite HMC-C025 (6-bit digital,
  0.5- 31.5 dB range, 0.5dB step size, max 10
  phase shift over full range, 25dBm max input. 3dB
  IL)
• Amplifier MiniCircuits ZRL-2400LN (30dB gain,
  24dBm output, 1.0dB NF, low VSWR (1.2), low cost
  ( 140))
• Directional coupler on input also couples
  transmitted power signal to diode detector
  (Agilent 84472B, -50 to -16dBM square law range)
  used for cavity field decay constant measurement,
  and to power meter (Agilent E4418B w/ 9301A
  sensor head (-60 to 20dBm) for cavity power
  measurements.

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Power Measurement Module
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• Power Measurement Module
• This module provides means for interfacing Pi,
  Pt, Pr, and PHOMA,B signals from the RF system
  and dewar top plate/cavity to the appropriate
  power meters and diode detectors.
• Pi, Pr and PHOMA,B Agilent E4419B dual channel
  RF power meters w/ Agilent 8482A power sensors.
  Range of -30 20 dBm (1mW to 100mW), with 300mW
  maximum input CW mode, 15W maximum pulsed for
  120ms.
• Pt Agilent E4418B single channel RF power meter
  w/ Agilent E9301A power sensor. Range of -60 20
  dBm (1mW to 100mW), with 300mW maximum input CW
  mode, 15W maximum pulsed for 120ms.
• Pi and Pr coupled to power meters via high power
  (500W CW) 20dB dual directional coupler at
  amplifier output. Signals also coupled after 20dB
  additional attenuation to Agilent 8472B diode
  detectors (-50 to -16dBm square-law range, w/ 1W
  damage threshold).

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High Power Amplifier/Switching Network
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• High Power Amplifier/Switching Network
• The amplifier network provides for the capability
  to switch between external 500W and internal 1W
  amplifiers. It also provides an interface for the
  interlock signals/RF permit from the PSS system,
  and contains protections element (circulators,
  couplers, loads).
• High power amplifier OPHIR Model 4046, 500W
  output, 58dB small signal gain, 10dBm max input,
  1270-1310 MHz frequency range, ALC bypass, fully
  protected (internally) for reflected power
• 1W amplifier MiniCircuits ZHL-42, 30dB gain,
  28dBm output, 5dBm max input, 700-4200 MHz
  frequency range
• DD Coupler Narda 3022-20, 20dB coupling, 30dB
  directivity, 0.3dB insertion loss
• High power switch Dow-Key 402-A280132A , 80dB
  isolation, 0.2dB max insertion loss, TTL logic,
  failsafe operation, rated for 106 cycles

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• High Power Amplifier/Switching Network - 2
• Load Bird Technologies 8201, oil-filled, 500W
  CW rating, over DC- 2GHz, low VSWR (1.1)
• Circulator UTE Microwave CT2574-N, 500W, 0.3dB
  insertion loss

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Attenuation Budget High Power Feed Need to keep
overall attenuation from HPA to dewar top plate lt
3dB (preferably 2.5dB or less) From amplifier to
top plate 4 cable inter-component (5/8
Heliax) 0.08dB High power switch 0.20dB Circul
ator 0.30dB Directional coupler 0.30dB Cable
to top plate (22, 5/8 Heliax) 0.46dB Cable to
cavity (Meggitt SiO2 , 0.270 OD) 0.90dB (incl
connectors) Total attenuation HPA to cavity
2.24 dB 0.25 ? Power delivered to cavity
280-300 W
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• Diode Detector / Signal Conditioner Module
• Signals for Pi, Pr, Pt are coupled via 10, 20 or
  30 dB couplers (depending on intrinsic signal
  strength) to diode detectors, for use in
• system calibration/commissioning
• measurement of cavity field decay time constant
• monitoring on oscilloscope
• Signals are conditioned using low-noise op-amps
• Diode detectors Agilent 8472B, w/ 200mW (23dBm)
  max input level, 1W input damage level, -50 to
  -16dBm square-law range, max output of 12.5mV.
• Signal conditioning amplification Combination
  of a three op-amp instrumentation front end, two
  buffered op-amp outputs, with LPF. Can provide
  over 30dB gain to yield signals on order volts.

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Infrastructure
LLRF
Cryo Rad Inst.
HPA SW
PC/PXI RF Instr.
HPA SW alt loc.
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• DAQ HW
• PXI chassis w/ embedded controller running
  Windows XP OS and with LabView 8.0 resident,
  provides a flexible, integrated, and efficient
  DAQ platform. Significant knowledge base in
  TD/TI Dept.
• PXI Chassis NI 1042Q, 8-slot, accepts PXI PCI
  modules
• PXI Controller 2GHz Pentium M processor, 2 GB
  RAM, cPCI Express bus, integrated USB (4),
  Ethernet, GPIB, RS-232 interfaces, integrated
  40GB HD, external CD-ROM
• PXI 6229 Multifunction DAQ 32 16-bit analog
  inputs (programmable ranges, 250 kS/sec), 4
  16-bit analog outputs, 48 bits of digital I/O, 2
  32-bit integrated counter/timers

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• DAQ HW- Interfacing and Control
• PXI system mutifunction DAQ board provide
  interfaces for
• Power Meters (3) GPIB
• Diode Detectors (3) analog input
• VCO error signal analog input
• Frequency counter GPIB
• Digital attenuator 6 bits D/O
• VM analog output (2)
• AM (RF pulsing) switch 2 bits D/O
• Transmitted power network amp switching (2) 4
  bits D/O
• LHe bath thermometry GPIB
• LHe level sensor GPIB
• Dewar pressure transducers (2) RS 232 and/or
  analog input (2)
• Radiation detector/monitor RS 232 and/or analog
  input

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• DAQ SW
• Multi-threaded state-machine architecture written
  in LabView (ported to LV8). Two distinct state
  machines (AB) B provides I/Q modulation _at_
  10Hz, A provides remainder of control, DAQ,
  utilities, analysis _at_ 0.5Hz.
• State Machine B (I/Q Modulator Control)
• Initialize
• Handshake w/ state machine A
• Write I/Q data to VM
• Return

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• DAQ SW
• State Machine A
• Initialize cavity id, type, filename, etc.
• Select dewar not implemented at FNAL (yet)
• Calibrate interactive cable calibration
  routine, w/ user prompts, help files, calibration
  data logging
• Set mixer level adjusts Pt network amplifier
  (out if Pt gt -2dBm), Pt attenuator, ensure Pt
  diode signal 1V, adjust f (via VM) if needed
• Optimize phase performs 10 phase sweep, look
  for Pt max
• Acquire CW data measures Pi, Pr, Pt, PHOM, f,
  calculates E, Qo, etc. and logs data
• Acquire decay data performs decay measurement
  of Pt, fits data, calculates E, Qo, Qfp, etc.,
  logs data
• RF pulse pulses RF at user-selectable rate
  period for FE processing
• AutoStep automatically sweeps through
  attenuation range to automatically generate Q/E
  curve (logs data)

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• Interlocks/Personnel Safety System
• An integrated system of interlocks (PSS) is
  needed to prevent exposure to ionizing radiation.
  This functionality will be provided by the
  AD/Interlocks Group. The present RF system design
  can easily accommodate these controls. The RF to
  a cavity can be disabled by
• Switching off LLRF drive signal
• Switching the RF path from 500W to 1W amplifier
• Switching off AC power to HPA
• Typically one wishes to have more than one means
  of disabling the system.
• Some conditions that personnel interlocks must
  rcognize
• Rad shielding open and 500W amplifier selected
• External (area) radiation monitors read above
  bkgrd
• In-shield dewar rad monitor reads above bkgrd
  with shield lid open

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Summary The proposed design is based on a proven
architecture that has successfully met
operational needs and exceeded original
throughput requirements. The modular nature of
the design permits independent testing and
optimization of the various circuits. The use of
COTS components simplifies the engineering effort
required, and provides a straightforward
optimization path. Duplicating the general
architecture of the JLab systems allows us to use
existing software that would otherwise require at
least 1 additional FTE of development. This
design approach leads to high confidence that the
system can be built and commissioned in
accordance with schedule needs.
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RF System Implementation Plan
J. Ozelis Fermilab/TD/Test Instrumentation
Dept.
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• Successful implementation requires that we
• Identify tasks
• Estimate task durations
• Plan activities
• Identify resources needed
• Identify resources available
• Address resource shortfalls/mismatches
• Resolve resource conflicts
• Track activities and progress
• Sounds simple !

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• Identify tasks
• Estimate task durations
• Plan activities
• Preliminary MS project schedule prepared,
  including completed tasks to date. Major
  milestones include
• VCO/PLL VM system test 1/3-9/07
• Full system testing (on load) w/ interlocks, SW
  mods 2/16/07
• Full system test /w cold cavity 4/30/07
• RF system is NOT on the VTS facility critical
  path
• cryostat delivery 3/15/07
• cryostat commissioning begins 4/9/07
• RF system ready for full system testing before
  3/1/07

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• Identify resources needed
• Identify resources available
• Address resource shortfalls/mismatches
• Engineering, design, testing 1940 m-h / 1.7
  FTE
• Fab/Assy 840 m-h / 0.75 FTE
• SW 770 m-h / 0.7 FTE
• PSS design, fab 384 m-h / 0.3 FTE
• Total 3934 m-h / 3.5
• Sept 1 April 1 time frame 1120 hrs ? 3.5 FTE
• FTE ? 1 employee _at_ 100 effort from 9/1/06 to
  3/30/07

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• Identify resources needed
• Identify resources available
• Address resource shortfalls/mismatches
• Eng, design, testing 1.7 Ozelis (.8), Nehring
  (.6), Powers (.1)
• Fab/Assy 0.75 TD/TI dept tech supt (.75)
• SW 0.7 TD/TI dept SW (.5), Nehring (.1),
  Grenoble (.1)
• PSS design, fab 0.3 AD Int Eng (.15), AD Int
  Tech (.15)
• Total 3.45 FTE
• Needed 3.5 FTE
• Manpower shortage of 0.05 FTE overall (0.1 FTE in
  Eng/Des/Test). This is certainly in the noise.
• SOW as addendum to JLab/FNAL ILC MOU prepared,
  awaiting approval, to formalize arrangement.

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• Project Status
• Design for LLRF is essentially finalized, can
  begin procurement and fabrication. Parts list
  70 complete.
• High power system procurement essentially
  complete all POs placed, most items received
  (amplifier delivery early Sep.).
• Instrumentation procurement at 80 - all POs
  placed, most items received (waiting on NA, dewar
  pressure transducers readout).
• DAQ platform PO placed, awaiting delivery.
• Software downloaded, ready for modification (some
  work begun).
• We are ready to proceed at full speed, upon
  approval