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The LIGO Executive Committee
Agenda for Monday July 24, 2000 will be:
(Meeting time: 10:30 am Pacific Time)
Open meeting 10:30 - 11:30
Special Items:
LHO 2K power recycled Michelson locked and Y arm ETM illuminated. Stay tuned...
No report this week.
WBS 1.2 LIGO Operations--Administration
From: Ed Chargois <chargois_e@ligo.caltech.edu>
Web pages for the DCC give simple how-to's for document numbering, easy access to the latest on-line documents, and search capabilities for the DCC database. Take a look. . .
From: Cleveland Mak <mak_c@ligo.caltech.edu>
From: Esther Cunningham <esther@ligo.caltech.edu>
Press here for ACCOUNTS
PAYABLE HISTORY DATA.
From: "Brambila, Ruth" <Ruth.Brambila@caltech.edu>
A lease is being prepared for a building to be used for storage space for the power supplies used in the beam tube bake. The lease is with the Town of Livingston, and is for three years at a cost of $1,500 per month.
Rita Torres
PLEASE NOTE: This report covers only three days since I took two days vacation last week.
Progress Period from 7.14 to 7.20
Accomplishments:
The following change requests have
been submitted:
| CR-990028 | WBS 1.1.3 | Beam Tube Enclosure Closeout | F. Asiri |
| CR-000005 | WBS 1.2.1 | Upgrade Pre-stabilized Laser | S. Whitcomb |
| CR-000006 | WBS 1.2.1 | Re-polish Core Optics Components | S. Whitcomb |
| CR-000007 | WBS 1.2.2 | Replacement of Optical Lever Lasers | S. Whitcomb |
| CR-000008 | WBS 1.1.4 | Cameras and Projection System at LIGO Livingston Observatory | F. Asiri |
| CR-000009 | WBS 1.1.4 | Cameras and Projection System at LIGO Hanford Observatory | F Asiri |
| CR-000010 | WBS 1.2.2 | Redesign Suspension Controllers | S. Whitcomb |
| CR-000011 | WBS 1.2.2 | VME Development System and Spares | S. Whitcomb |
| CR-000012 | WBS 1.2.2 | ASC/LSC Rework | S. Whitcomb |
Copies of these change requests have been distributed to memebers of the LIGO Change Control Board (See LIGO-M000176-00-P). Two change requests, those for cameras and projection systems are for information purposes only (they fall below the threshold for CCB review and approval) and will be entered into the budget baseline.
Press for the latest Contingency Needs Projection.
From: Kris Duncan <kris@ligo.caltech.edu>
From: Ed Jasnow <jasnow@ligo.caltech.edu>
A meeting was held on Tuesday, July 18, with the Caltech Controller, Al Horvath, his property consultant, Nancy Nerasaki, and the Manager of the Office of Sponsored Research, Dick Seligman. Attending for LIGO were Florence Kaufman, Ed Chargois, and Ed Jasnow. The purpose of the meeting was to determine the methodology of tracking LIGO property for Caltech. It was agreed that the current LIGO property database being kept by Ed Chargois would be the one used by Caltech. It was also agreed that, in accordance with the cooperative agreement, the intent at the time of purchase would be the criteria used to determine where title resides in equipment.
General items:
--------------
(F. Raab)
Efforts this week focused on locking the power-recycled Michelson. Stable
locking was achieved last weekend and efforts to improve alignment behavior
have helped. Now work is moving toward getting the Y arm to resonate as
well.
Doug has been doing staging work in the end stations to prepare for
4K optics installation. Corey and Hugh are converging on a measurement
of the BSC stack transfer function.
The Port of Benton is reviewing proposals to mine gravel at the north
end of Richland, about 10 miles from LIGO. Alan Rohay of Batelle has been
invited to some of the meetings and he has expressed concern that, in the
absence of hard data on the the transmissibility of noise through the local
terrain, it is hard to convince the Port not to proceed. Our SST team from
Kamiakin High School has been working with Hugh Radkins to learn how to
make seismic field measurements in preparation for characterizing impacts
of man-made noise sources. Having completed their measurements characterizing
the effects of traffic on a bump in one of our access roads, their next
assignment will be to characterize the ACME gravel mining operations in
the south end of Richland.
We are planning a LIGO Public Lecture for the local community to kick
off the August LSC meeting, featuring talks by Kip Thorne and John Wheeler.
Wheeler has dual ties to Hanford history. In 1943, he was the lead scientist
for the first plutonium production reactor, built at Hanford. Later, he
gave birth to much of the science that LIGO will seek to uncover. Wheeler
will be returning to Richland in August for the LIGO Science Collaboration
meeting. While here, he will be signing his autobiography at CREHST, Sunday
August 13, 3 to 4:30 p.m. He will also appear at a public lecture
with Kip Thorne at Battelle Auditorium, Monday August 14, at 7:45 p.m.
Bake Oven:
----------
(K. Ryan)
Vacuum Bake Oven A load #97, consisting of Elliptical Baffle Components,
Table Clamps and OSEM Cables, was released on 6/26/00.
Load #98, consisting of misc. COS parts & fasteners and misc. small
optics beam dump and mirror mount components, should begin on or before
Monday, 7/24/00.
Most of the modifications to oven A's control panel have been made but
not all of these have been tested.
Fabrication of Vacuum Bake Oven B has been delayed as the result of
having to change vendors. I expect oven B to be available sometime
in late August. Oven B will be used for
small loads, i.e. fasteners, small plates and brackets, small optics
and individual large optics and should improve turnaround times by ~30%
or so.
Seismic Systems:
----------------------
(M. Guenther)
CAS Status
All CAS cables have been installed on BSCs 1, 2, 3. Position encoder
readouts have all been tested successfully on these BSCs.
Pneumatic assembly is continuing; we are expecting our back-ordered
1
micron filters from Festo the week of 8/7.
OPTICS/COC/SEI INSTALLATION: In the course of COS installation we have
discovered that the BSC tables are out of plane by as much as 0.015" in
12". Not until after moving table weights around did we discover
this. This of course makes the use of levels problematic; the appearance
of being level depends upon where on the table one affixes the level!
The concern now is that we have perturbed the alignment of our ITMs, so
we are removing the spoolpieces in order to re-setup the ISC theodolite
and check their alignment. (Jonathan Kern)
FACILITY: Met with Mr. Derral Jones, Mayor of Livingston and inspected the proposed storage building in town of Livingston. Finalized the term of lease and list of items need to be fixed in the building as condition of lease. Mr. Jones agreed to submit in writing the lease term. I have cordinated our discussion with Ed and Gerry.
Met with John Desmond and Craig Sauvac the Architect for the new staging building. We have work out he arrangement of the Auditorium. They will finalize the architectural drawings for review by next Monday, July 24.(Fred Asiri)
Covered elsewhere
Covered elsewhere
| Installation
& Commissioning:
Livingston |
Other Science/Engineering
Activities:
Issues/Concerns |
See also the Installation web page
Depending on alignment, the PRM frequently showed periodic alignment fluctuations which produced huge modulation of the power inside the cavity. We had initially suspected 1 micron light coupling to the suspension local sensors, and had done various tests such as reducing the input light power and disabling and/or lowering gains on the local dampingloops, but had seen no clear effects. Then Bill K's keen eyes noticed an increase in the beamsplitter's (BS) optical lever signals when the PRM was locked; since we are sending no control signals to the BS, we began to again suspect 1 micron light coupling. This time we turned off all 4 damping loops on the beamsplitter, and this seemed to be the key: the periodic power fluctuations essentially went away, leaving only the 10-20% random fluctuations that we had seen from time to time. So it looks like the driven oscillations were caused by 1 micron light coupling into the beamsplitter local sensors, and that we were finding places by adjusting the overall alignment where less light was scattered into them. Bill K also notes that previous measurements of 1 micron light coupling into all the LOS local sensors showed a higher coupling to the BS sensors than the other optics. Since this initial test we have turned the BS damping loops back on, but reduced the gain in each loop to 1.0; this seems so far to be small enough to avoid the light-coupling driven fluctuations.
The measured recycling buildup was a factor of ~7 for the carrier and about a factor 4 for the sidebands, in fairly close agreement with what is expected for the as-built cavity without the thermal lensing in the ITMs that will come into play when the full power is used in the interferometer.
Since we made progress in understanding and curing the alignment oscillations, and had success with locking on the RF sidebands (using either the AS port or the Reflected Q-phase demod signal), we decided to go ahead and open up the Y-arm to look for the beam. With the PRM locked on the carrier, we immediately saw the beam on the lower left edge of ETMY, so the input beam pointing was still reasonably good. Rana adjusted the angles of ETMY and ITMY to get a circularly symmetric beam as seen by the ETMY transmission camera.
We currently don't have the software and hardware to send a LSC control signal to ETMY, so we couldn't try locking the arm cavity; there is also currently no quadrant detector on the ETMY transmission beam. So we couldn't do much more, but we did learn one important piece of information: when we initially operated this system with the PRM locked on the RF sidebands, with any reasonably close alignment of the ETM, the cavity resonances would destroy the PRM lock. This is not good because in the lock acquisition scheme we are supposed to be able to transition from the PRM sideband lock state to state 3, which adds an arm cavity locked to the carrier. Then we found we could lower the Michelson (lm) loop gain (by a factor of 2-3) to keep the PRM stable as the cavity went through resonances.
Before the next attempt, we will get the LSC hardware/software going at Y-Mid, and get the new ETMY transmission monitor assembly together.
I also hope to load and run the new DAQ software later this week.
A new optical layout for the 40m Lab PSL has been initiated. The current table will be somewhat more crowded than initially thought.
Rich Abbott
Further testing has revealed
considerable insight into the behavior of the frequency control servo.
Several new topologies have been tested and each has brought me significantly
closer to a robust solution. Several more tests in the Lauritson
lab are to be performed.
The machined parts for the last two ETM transmission monitors (for Washington 4K) have been completed. I will finish the assembly of these two and ship them sometime next week.
Jay Heefner
Work continues on the various
AC osem ideas, but there is nothing new to report.
No report received.
Vacuum/infrastructure: Ed K. completed some annulus leak rate tests
and
characterized the flow rate of our new HC/particulate/water vapor
trapping backfill filter.
Seismic isolation: Ken M. began mobilization for installing the seismic
isolation external supports and some internals. Useful advice was
obtained from LLO and LHO experts (as well as generous offers of
much-needed help).
Experiment design & test goals: Ken, Mike and David developed a
baseline
interferometer optical and control plan which we think strikes a good
balance among the mission goals proposed by our advisory panel. We
started optomechanical design (Ken), noise analysis (David) and control
systems topology definition (Mike). We will seek feedback from the
Lab
and Collaboration at the August LSC meeting.
Matt participated in the Power Recycled Michelson lock.
Biplab worked with Brad and Rick on effects of higher order modes
on error signals and noises in Frequency Stabilization System
(FSS) of PSL that includes the reference cavity.
>> Adlib code
Biplab, Luca and Hiro worked on the lock acquisition simulation with
misalignments. Luca found that very small misalignment make the
system too hard to lock, compared with the case with no misalignment.
The problem was traced to a possible bug in the simulation code.
Biplab looked into the case and make a temporal fix.
During this study, the problem of the slowness
of the simulation
makes it take too difficult to solve the problem.
To simulate
one second, it takes a few 10 minutes and to
see if once case locks,
it takes several hours. This problem needs to
be solved by both
software and hardware. None has been achieved
yet, because of
lack of manpower, especially the software improvements.
This will become a more and more serious problem
as we go into
the detail simulations including more modes.
Biplab could generate noise-curve of only W2K arm including
shot, seismic and thermal noises. Some questions of detail still
to be sorted out.
Hiro wrote a new input module to read data from a disk file. This
is used y Biplab with Rick and Brad to read the data of the simulated
reference cavity mirror motion generated by G.Cella. This simulation
is used to test the noise caused by the motion of the reference cavity
of PSL table.
The idealistic solution is to use MSE fully integrated with e2e.
G.Cella has written a code providing API of MSE for e2e when
he visited here last time. Unfortunately, the integration has not
been completed because of lack of man powers.
>> Hardware performance test on Alpha and Pentium
Chris Lee of CARA helped to run e2e simulation (lock acquisition case)
on his Alpha machine to measure the performance. On his Alpha
workstation DS20 and XP1000, running at 500 MHz, the speed was faster
than sargas
by factor of 2.53. The same code was run on m71 (500 MHz
Pentium) to
find the speed gain of 2.11.
>> Alfi
Ed and Bruce are working on alfi. There are several issues to be solved
before anything new are to be added/improved.
Software Systems (Blackburn)
The CSCC meeting outside Athens included a significant number of talks on
signal processing and computation. The signal processing talks were weighted
towards applications of wavelets and time-frequency methods. Many of these
applications seemed to be motivated by trend instead of applicability of
wavelets and such. The signal processing community also presented several
talks on advances in mathematical approaches for digital filter algorithms,
though most of these were applied to hardware. The focus was to reduce the
number of cycles needed to apply a digital filter (using mathematical
transformations on the filter) and on reducing the number of interations of
a digital filter to detect oscillations inherent in the filter design. The
motivation behind these projects being to extend battery life in cellular
phones and other digital hand held communications devices. One interested
speaker presented the trend towards more and more expensive testing costs
for large integrated software system, as much as 70% of software costs are
in testing for such environments now. All in all the conference proved to
be interesting but noticably less dynamic than a typical GW or LSC meeting.A new memory leak in the LDAS software was identified this week. The leak
may have existed prior to this week but was not exercised until we had the
support in the frameAPI to concatenate frame data into ILWDs via user commands
from the manager.The dataConditionAPI has now been started up and run for several hours on the
Quad PentiumIII box. This marks the first LDAS API to be run on a LINUX platform
and the first to run on the quad PIII. The user command for this API is still
under development and only a handful of action functions are available for the
algorithm. This does make the group a bit more at ease about being ready for
the Mock Data Challenge at the end of the month.The wrapperAPI has now been shown to run with the binary inspiral search
dynamically loaded shared object library from UWM on linux platforms. In fact,
the results produced by the run are in agreement with other codes that perform
the search. This is a major success for the parallel analysis working group
and even though much work remains ahead on this project they have demonstrated
a very important component of LDAS to work.A new test script is being developed to run nightly which will test each LDAS
API for start up CPU and MEMORY usage to be used as a first look into the
process loads and derivatives for APIs as they develop and evolve. It will also
test that the API can actually be started without aborting nightly.The multi-client GUI interface to the controlMonitorAPI for LDAS is now
working. The server side can distinguish unique requests from separate users
to monitor LDAS and present the requested information appropriate the each
request.The problem with NaN (Not a Number) reads in the ILWD that were found last
week have been tracked down to the standard library in C++. The fix was to
use C's standard library functions instead of the iostream from C++ to be
able to correctly handle NaNs.
Hardware Systems (Anderson)
1) Initial installation of Solaris 8, GigE cards and D1000 disk array
in the two new LDAS E450's at LHO is complete. Work is ongoing for the
installation of LDAS software as upgrades for the current U10 dataserver
and U10 metaserver.2) The beowulf rack equipment from LLO has made it to LHO and awaits a final
decision on the floor plan before installing. The CIT development rack
installation is 90% complete.3) The gateway to the current LDAS system at Caltech has been renamed
from ldas.ligo.caltech.edu to ldas-dev.ligo.caltech.edu to reflect
its function as a development system and to make room for the installation
of the Caltech production system starting in August, which will have
the gateway named ldas.ligo.caltech.edu.4) A dual processor Linux box has been added to the LIGO GC network
with the necessary configuration to access LDAS software and be used
without need for coordination with the LDAS programmers as a software
test-bed by LSC programmers. It is named ldas-pcdev1.ligo.caltech.edu.
Expect a similarly named Sun computer (ldas-sundev1) in the near future.
Data Analysis Activities
>From Philip Charlton:
Main activities have been preparation for the Data Conditioning API
Mock
Data Challenge which begins in the last week of July.
I have also been working with Antony Searle at ANU towards getting the
LDAS system to build on Sam Finn's machine at Penn State.
Last week I finished the real and complex versions of the fast exact
quadratic chirp transforms and sent them to Julien Sylvestre. He will
be integrating this code and that developed by Jeff Edlund into his
code
for analysing the data from the engineering run.
>From Jeff Edlund:
I completed the first draft of the fast approximate chirp transform
for a
phase function with an arbitrary number of parameters. This version
improves upon the original code from Rick Jenet by doing many of the
FFTs
by inspection when the sequence to be FFTed has only one non-zero
element. I tested it with 2, 3, and 4 parameters. The chirp was found
exactly in the 2 term case. With 3 and 4 parameters, accuracy
was limited
by memory. Further testing is required.
I'm working on measuring the execution time of the algorithim at various
data sizes to determine the order of the algorithm and compare the
execution time with that of Rick's code.
> Lazzarini
I am working with Sam Finn on a short note for publication that deals
with an
improved measurement of the narrowband stochastic background that will
be possible
using the LLO+Allegro pair. The idea is to modulate the background
by rotating Allegro
periodically (once every ~1/2 year, e.g.). Unfortunately, LIGO I senstivie
at ~1kHz is not as good as Allegro's.
Nonetheless the technique allows one in principle to deduce correlated
terrestrial backgrounds.
MIT:
Still preparing for new computer room installation. Detailed information
about
the room has been sent to Albert and Larry.
Livingston:
Working on their mirror of the DCC.
Continuing work on the network backbone.
Hanford:
Nothing to report
CIT:
(Barbara)
- Installed a first iteration of a web report for the CostBook.
Installed
changes to CostBook web forms for Management resource. Imported
updated
tables from P3.
- Made changes to LDAS images and scripts for new server arrangement.
Added/updated links for User Commands, LAL, and LDAS Build.
- Made web site changes -- new page for science seminar transparencies,
updates to fellowship pages, couple of LSC documents.
(Lisa)
- Rebuilt the OS on graffias. Learned how to set up a NIS+ client.
This has
also gotten me into looking at how NIS+ and NFS mounts are working
in our
cluster. Since there are a couple of areas in which the NFS mounts
need to be
changed (like Luna), I am spending a lot of time trying to really get
a good
picture of how all of the pieces are coming together.
- Spent time working on the PC's in Wilson House. Rich Abbott
is getting moved
off of his old box. We should be able to recover that for someone else
by the
end of the week. Spent a little time with Mohana clearing up some lingering
issues. Reworking the basic network setups on the PC's this should
clear up some
of the network issues at Wislon House.
- The new Cadence software and the hard disk for it have arrived.
I will be
working on getting that installed this week. We have another
temporary license
to use while the installation takes place.
- Still plugging away at getting specs and prices on an upgrade for
our Remote
Access Server. I should have all the info we need to make a decision
today.
- Finished running new network cables and hubs in our office.
(Samantha)
- Built a new PC for 40M lab.
- Worked on more documentation.
- Built a machine to test WIN2000 on.
- Still working on NT server items such as a new backup method.
- Backed up files for people.
- Burned a number of CD's.
- Testing norton anti virus (installs just fine on every computer tested
on
except mine). Once our licenses for McAffee expire we will switch to
Norton on
Caltechs site license.
Picking on Ed Chargois.
(Suresh)
On Vacation until August 23rd.
(Larry)
Finished up some cabling in a few different areas.
Spent a great deal of time working on budgets and procurement plans.
Resolved a number of issues on the servers. Going back to make sure
the units
are rebooted at least once a month just to fsck the disks and clean
out old
processes. The reboots will be scheduled after the monthly backups.
Worked a number of procurement issues and still working with Ed C.
on getting
some of the old equipment cleaned out.
Went over the network situation for the Lab Room in Bridge that the
CDS group is
going to occupy.
Helping Lisa and Sam become more familiar with the server setup and
network
setup here at CIT.
Resolved some licensing issues with Cadence.
Peter King
LIGO II PSL
The first draft of the LIGO-II PSL WBS dictionary has been
completed.
Rich Abbott
Began process of cost estimation for LIGO II frequency distribution
assuming a similar requirement to the LIGO I system
From: Jordan Camp <jordan@ligo.caltech.edu>
The following is a status report on the sapphire development program:
Polishing: 2 half size test samples have been
sent to CSIRO for optical
characterization, including measurement of optical
inhomogeneity. Preliminary
measurements showed about 0.15 wave peak-valley
inhomogeneity in transmission
through the substrate, an encouraging number.
After characterization, the optics
will be polished to see if they can be brought
to specification for surface
figure, microroughness, and homogeneity.
Q measurements: Q's of bare polished sapphire
pieces have been typically better
than 2x10^8. Measurements of the effect of attachments
and coating on Q are
pending.
Coating absorption: absorption measurements of
coatings of both c and m axis
sapphire have shown < 1 ppm absorption.
Coating birefringence: a preliminary experiment
which measured resonant
frequency spacings through a Fabry Perot cavity
showed about 10 mrad
birefringence for a 100 ppm transmission coating
on an m-axis sapphire
substrate. This number was consistent with an
earlier experiment by Blair, and
is probably low enough to permit the use of m-axis
coated sapphire, but further
work in mapping the birefringence is necessary.
Substrate absorption: measurements of substrate
absorption have been made of 4
different starting materials from Crystal Systems,
at 3 different places in each
boule (to look for possible segregation of impurities).
The data shows no
correlation of material or boule location with
absorption. The average value of
absorption is 80 ppm/cm. Further measurements
will involve zone refining of
sapphire boules to produce higher purity material,
and annealing studies to
examine the effects of oxidation on the absorption.
Measured samples will also
be sent out for spectroscopic analysis to see
if any correlations can be made
with absorption and chemical composition. We
have also received a couple of
sapphire samples from SIOM, China which will
be measured for absorption.
LIGO II ISC (Zucker, Bork, Ouimette, Heefner, Fritschel, Mavalvala,
Sigg, Abbott)
-----------------------------------------
MZ agreed to provisionally take the lead organizing LIGO II ISC
definition for the proposal. Please copy Mike (and continue to copy
Dennis, Gary, David and Peter Fritschel) on significant LIGO II ISC
interface & requirements issues.
Began drafting of reference design document and WBS to support proposal.
Significant input on modulation & sensing topology will be required
from
the next Systems/Config summit and the following LSC meeting discussion.
We have enough to start on describing the actual controls
electronic/software implementation (in a "plant-independent" way at
least), much of the alignment system, photodetectors, and some top-level
requirements definition.
From: Helena Armandula <ahelena@ligo.caltech.edu>
LIGO II coatings:
A conference call with REO and LIGO management will take place next
week to discuss the possible involvement of REO as LIGO II coating's supplier
and to formulate plans.
SIlica bonding:
(See P. Willems report)
Stiff isolation system (Sam Richman, Jamie Rollins)
Jamie has the Siglab system working and we will now use this to do additional characterization of the isolation prototype. Sam beginning to write up descriptions of the instrumentation and control system of the prototype, as well the measurement procedures.
From: Riccardo DeSalvo <desalvo@ligo.caltech.edu>
Yesterday removed the LIGO IP from the space allocated for Minos,
reassemble of IP during this week
Lisa, Gigio, Paolo
Ready to test LVDTs stability in oven.
Computers breaks down repetitively, cause unknown, reliability is a
serious a problem for long term Creep DAQ.
Oven stable within +/- 2 degrees C peak peak over many days.
No internal/external temperature correlation.
Gigio, Paolo
Tested and calibrated and assembled LVDTs for oven test.
Gotten additional DAQ computer in working order.
Prepared cables for DAQ.
Akiteru
IP transfer function looks understandable, and plateau lowered possibly
to 35 dB, counter weight still to be tuned, too heavy for good
plateau. Some problem with perpendicular direction sensitivity
of
commercial accelerometers, maybe will have to make TF with LVDTs
instead of accelerometers.
Hareem
Computer for filter thermal stability measurements working again after
removal.
Located by-metal strip/coil manufacturers for GASF thermal drift
compensation.
By metal strips easily deliver the 20 to 60 g/degrees lift necessary
to
compensate the GASF springs thermal lift loss.
Brett
Stepper motor noise reduction effort, not easy to do cheaply,
silent
steppers probably useless because steppers would be used with IFO off
lock.
Stepper motor driver PCB to be delivered soon. Working on VME
software.
Soy
Acoustic emission setup ready to run, starting connecting noise pickup
sensor on stressed blade.
Susha
Simulation still produces too high vertical resonant frequencies (2
Hz
instead of 100 mHz). Found bug and now, at least, increased radial
compression correctly yields lower resonant frequencies. Looking
for
working point.
James
First MGASF transfer function, hoping to reproduce earlier results
next
week and then proceed with further measurements.
Virginio
Rediagonalised IP MIMO under different conditions before disassemblying
of IP
ChenYang
Preparing Marconi circuitry.
Alessandro/ Pisa technicians, Galli&Morelli
Tested new accelerometer, kinematically perfect but still lower quality
factor than expected. Earlier prototype with 5000 series Aluminum,
this
one with 2000 series, it is then no bulk problem. Likely
coming from 2
micron melted layer left by EDM on two faces of 50 micron flex joints.
Will try double cure:
thermal annealing and tempering process (under vacuum) to eliminate
recrystallization stresses
resuming electro polishing to eliminate presumed offending layer.
These tests to be made first on old prototypes to minimize risks.
Still accelerometer more than adequate for present inertial damping
use
(thermal noise problem only relevant in advanced inertial damping and
performance monitoring uses).
Put 3+1 accelerometers in production for TAMA IP damping, mechanics
machining e.t.a. this Friday, e.d.m. machining e.t.a middle
of next
week.
Accelerometer readout electronics modules OK, e.t.a. next week,
populated PCBs will be sent without NIM module mechanics, need
to
procure NIM modules in Pasadena.
In Pasadena disassembled and shipped accelerometer back to Pisa for
risky tests.
For additional information about this report, contact sanders@ligo.caltech.edu