Our new ADSC Q315 diffractometer system was installed 18 January 2002.  The CCD-based detector is 315mm square and is mounted on a specially designed kappa-axis goniometer.  This detector reads out in approximately one second, and will easily resolve 400 orders across its face.  With some care, it will resolve over 500. This data-collection system was purchased with funds provided to the BNL Biology Dept. and the NSLS by the NIH National Center of Research Resources, the National Institute of General Medical Sciences, and the Department of Energy Office of  Biological and Environmental Research.

 

Overall:
The numbering system is a little bewildering.  Each detector module has a number in the 200-300 range.  They assembled the modules and put them on the shelf, then selected them for our detector.  Then each readout electronics from PixelVision has a number in the range 3000-4000.  Each readout computer has a number either 0-4 or 1-5, depending whom you're talking to.  Just keep calm and all will be revealed to you.  There's precious little documentation for the whole system.  We'll just try to figure it all out, write it down, and share it among the fellow users.

Detector:
Typical phosphor/taper/CCD.
Uses large but not largest tapers -- 150mm.  Gives 105 square.  (Biggest are 165, I think).
Phosphor deposition designed by Eric Eikenberry (now at SLS).  Chip bonding is partly by Walter Phillips
Chips are Thompson 2k, 4-readout chips.
Readout is approx. 1 sec. full readout.  1/2 second 2x2 binned. There is some talk about 2x2 software binning -- I don't know how this works.
Most of the readout electronics is in the detector head.  It's designed by a company called Pixel Vision that is closely coupled with ADSC in some way.  Communication with the outside world is with a proprietary fibre-optic channel -- one channel for each 4-readout chip.
Peltier (thermoelectric) cooling goes to -45 from a water temp. of 12C!!

There is elaborate strain relief for all of the cables coming into the detector head.  Notice that there are nine 3/4" power cables coming in, and nine pairs of fibre-optic cables for control and data transport.  One MUST wear a grounding strap to get into the rear of the detector.  There is a ground bus at the bottom of the enclosed panel for the bananna plug of the grounding strap.  There are about four panels that must be removed to install or remove cables.  Assemble it from the bottom up; dissasemble from the top down.  The exception is that the three fibre-optic pairs along the left side should go on first because they're hard to reach.  The cables have a bayonet mount that twists off ccw.  The locating pin goes at 9 o'clock; the bayonet slots go at 12 and 6.  Each  cable has a polyethylene cap.  Each socket has a bayonet-mount cap that comes off ccw.
The power cables also get a quarter twist cw to put on; they're very hard to get off.  Push and turn ccw.  Don't forget the grounding strap.
 

Diffractometer:

The diffractometer was made by Chuck Strouse of Crystal Logic, Inc., of LA.  It has a kappa-axis goniometer, specimen-to-detector adjustment, and two-theta tilt.  The omega and kappa motors are driven to provide slightly better resolution (0.0005 degrees per step) than phi (0.001), but phi is driven well enough for ordinary data collection and is the default.

The theta drive is a cunning arrangement where the detector tilt-table is supported at the back by a rotary bearing, and at then front by a roller that rides on a cam.  The lift is counterweighted -- 100 lb of lead are suspended on the back side of the tower by the bicycle chains.  To remove the lead blocks for some reason, the back panel should be removed from the tower and wood blocks should be inserted to support the lead bricks.  When the chain is relaxed, the linkage can be removed.  There are two 2-theta limit switches -- see the instruction manual.

Control electronics for the diffractometer are housed in the back panel of the machine, accessible from the back.  Principal motor control is by a CompuMotor controller.  Other electronics are assembled by Crystal Logic.  These currently are accessible through a serial port to the host computer, although an ethernet line is available.  It's probably a good idea to turn power off on the diffractometer if the serial line is to be disconnected or connected.

The limit "switches" are all "soft" in the sense that some software has to recognize that they have been violated.  The most egregious example of this is the light curtain, which monitors approach of any object within about 1/2 inch of the detector face.  There are also far and close limits for the detector distance.  The close one has been adjusted to allow a closest approach of just under 90mm.  There's a clever (and possibly too conservative) set of limits for the combined omega/kappa motion that keeps the crystal axis from touching the collimator.

All axes in the detector need to be "homed" when the power is put onto the diffractometer.  Possibly this homing operation should be performed periodically in the absense of adventitious power drops.  We are working to have cbass detect when homing should be performed, and to tell you when it's completed.  The strongest evidence that something should be done is that the measured distance will be zero!!

There are three ion chambers (ICs) to monitor beam intensity.  There are four half-slit shutters that close off either the top half of the beam path or the near-side half.  See the photo below to the right.  The IC controllers are in small black boxes that contain also a microscopic high-voltage supply to provide bias for the IC.  The control box for the IC in the collimator is shown below left.  It has a selector for the bias voltage.

A convenient output from these ICs is a voltage that is proportional to the flux.  The signal is shown above left being taken from pins 4 (signal ground) and 5 (voltage ~ to flux).  We feed this into the V-to-F (voltage to frequency) converter at the beamline control station.  A slight weakness of the system is that the dark output (the voltage on pin 5 when there are no x-rays in the IC) needs to be adjusted by hand, and it's actually a little difficult to do.  In general, one should take the black cover off the device shown above/left, monitor the voltage across 4/5, and using a plastic Phillips screwdriver or one with all but the tip insulated, turn the little potentiometer that is obvious in the box to get the smallest positive voltage possible.  One can monitor the digital output on the V/F converter to see that there is some small positive number present when there are no x-rays.

The view at the x-tal position is shown above left.  We show the position with omega = kappa = 0.  In various photos one can see two telescopes, coming in 45 deg from the horizon and 90 deg from one another.  The top one has a small objective lens, the lower one a large one.  Although both are "zoom" instruments, they should be kept at low and high magnification respectively.  Each has an electronic crosshair.  Adjustment of the one for the large (Infinity) microscope is described in the X12-C documentation.  The other one is different, and I partly understand it.  Press the padlock button and hold it.  In the upper right of the TV screen one will eventually see "hold," "1," and "2" that cycle one to the other.  One of the lines displayed is "1" and the other is "2."  Press the up/down/left/right arrows until you get what you want.  Obviously, leave it with "hold" in place.

Illumination for the telescopes is a problem.  At the moment, to suspend an illuminated index card in the path of the Infinity works ok.  The other telescope is looking straight at the black screw that drives the diffractometer.  Prop an illuminated white card on that in the path of the telescope.

There is a small control panel at the right hand of the operator standing in front of the crystal position.  The STOP button should do just that for any motion.  The catch is that things may need to be restarted in some complicated way.   Immediate control of all five axes is at hand; try it for all but 2-theta.  There is also a jog+ and jog- button.  This rotates phi by 90 degrees exactly.  The obvious crystal-alignment protocol is to set phi so the sleds on the goniometer are parallel to one microscope.  Align the crystal to the vertical cross wire in the low-mag microscope with one jog, then do it again with the high-mag with two-three more jogs.  Users will have to concentrate on which sled they're moving and which screen they're watching.  Sorry.  The downside of the configuration of switches is that there is neither a readout of the axis positions nor a quick way to send 2-theta, kappa, and omega to precisely zero.  We're working on that.

There is a crude Z axis for the goniometer which can be used in an emergency when the throw of a goniometer-head z axis is inadequate.  There is a simple (metric) set screw locking the Z-axis screw.  It is located on the side of the phi drive, roughly at the 50-deg mark on the phi scale.  Loosen this; put the goniometer-head Z at its midpoint.  Drive the screw in or out to get close to the right position.  Then lock the screw again.  IT IS A NYLON-BACKED SCREW.  DON'T MAKE IT TOO TIGHT.

The beamstop carriers and beamstop supports are shown in several figures.  There are four diameters in the kit.  They're mounted on a high quality spring steel, and are on steel-lined aluminum bars intended to be placed on the micrometer-driven magnetic mount.  There is only a magnet to hold the bar up; it must be pressed against the back edge to compete the positioning.  The magnetic mount has been carefully adjusted to make it parallel to the beam.  A very satisfactory way to align the beamstop to the beam is to slide it up against the snout of the collimator.  Then it can be moved downstream so a crystal can be put in place.  I suggest putting it first fairly close to the x-tal, then moving it back as the images suggest finer adjustments to the position.  I find this is extremely easy to do.
 

The collimator is made to have replacable apertures, a selection of which are found in the toolkit.  (Please don't lose these, they're a pain to construct.)  The collimator tube also carries the ion chamber between the two apertures in the white ceramic insulator.  Notice that some lead tape has been added to the collimator: a collar around the shaft, and a strip to cover the exit slot.  Collimation may be changed with a specimen in place.  To change collimation, remove the strip of lead tape from the exit slot, loosen the holding screw a lot, and lift the collimator and IC assembly straight up.  If there is no specimen in place, the collimator can be drawn straight out of its channel with a small looseningof the set screw.  The limiting aperture is held in the upstream end with a small setscrew.  The Huber or Hampton goniometer-head-key has the right allen key.  We recommend 200/300 microns in the upstream/downstream positions respectively, or if x-tals are small, 100/200 microns.  The upstream allen screw must be put in facing upwards!  When you tighten the holding screw, remember that  IT IS A NYLON-BACKED SCREW.  DON'T MAKE IT TOO TIGHT.  At the moment the down-stream aperture should be held in with a tiny piece of tape.  Some other solution is on the way.
 
 

Power Supply / "Firewall":

 

ADSC have found that it pays to be obsessive about noise, which is partly why the communication is all by fibre optics.  To help combat noise, power comes from a 208-> 115V transformer, seen on the floor at the back of the cabinet above.  The three power supplies shown each have four channels of potential output; one is left as a spare on each one.  The vacuum pump for the detector head, and the water chiller for the Peltier system, both take power from this.  In our case, the nine heavy cables for the detector modules go into the feed-through behind the cabinet, the other cables go through the nearer feed-through.

Connecting these up is straightforward.  Power up of the system is begun firstly by throwing the black mains switch, top left, and then by hitting the yellow button at the top right.  This starts up the vacuum pump.  This must be going and the vacuum must be good before the water cooler should be started.  The vacuum indicators are at the top of the console here.  The water-chiller should be powered up in the usual way -- plug it in and turn on all the switches.  When water is flowing (monitored by a Proteus unit, and indicaed by lights to the left of the yellow button), the power may be applied to the CCD modules themselves -- this power will be used for readout and Peltier cooling.  The three switches should be turned on one at a time with a few-second wait between.

A GENERAL PROCEDURE FOR POWERING DOWN THE Q315

1) quit 'cbass'
2) on Q315 PC rack, quit 'remote operate detector' on each of 9 PCs (need to press green or red buttons above to shift between PCs)
3) on Q315 PC rack, start 'operate detector' on each of 9 PCs (info will scroll; will read 'any_fail: 0', or something like that, when each is ready)
4) on Q315 PC rack, PC #0, start 'quantum console' connect to detector enable temperature control ramp to 10 ⁰C
(careful: do NOT set temp to 10 ^oC; rather, ramp it; if it warms too fast, it could crack the chips)

5) after they all reach 10 ^oC, quit 'quantum console' and quit 'operate detector' on all 9 PCs
6) go to power supply behind hutch. towards the bottom are 3 controllers; each has 2 buttons -- the upper one is the temperature control, and the lower one is the power. if we consider button #1 as being the lowest button on the lowest controller, and button # 6 as being the highest button on the highest controller (see picture above), turn off buttons in the following order: 6, 4, 2, and then 5, 3, and 1. ie. turn off things top down, first the temperature control, and then the power. Unless there are explicit instructions, do NOT turn off the main power or mess with buttons on the top!!! (we want to avoid disasterous problems with the detector vacuum, etc.)
7) You are now able to switch fiber optic cables, etc., per instructions.

A GENERAL PROCEDURE FOR POWERING UP THE Q315

1) ensure on the Q315 PC rack that all the PC's (9) are on
2) go to power supply behind hutch. towards the bottom are 3 controllers; each has 2 buttons -- the upper one is the temperature control, and the lower one is the power. if we consider button #1 as being the lowest button on the lowest controller, and button # 6 as being the highest button on the highest controller, turn on buttons in the following order, waiting 15 seconds between pressing each power button: 1, 3, 5, and then 2, 4, and 6. ie. turn on things bottom up, first the power, and then the temperature control. Unless there are explicit instructions, do NOT press the main power or mess with buttons on the top!!! (if the main power had been off, please see other documentation) (we want to avoid disasterous problems with the detector vacuum, etc.)
3) on Q315 PC rack, start 'operate detector' on each of 9 PCs (info will scroll; will read 'any_fail: 0', or something like that, when each is ready) (need to press green or red buttons above to shift which PC)
4) on Q315 PC rack, PC #0, start 'quantum console'
connect to detector
enable temperature control
set temp to 0.0^o C
when they all reach 0.0 (will read 'final ...'), ramp to cold operating temperature
5) when they all have reached their final temp. (about -45 ^oC), quit 'quantum console, and quit 'operate detector on all 9 PCs) (careful: do NOT set temp to cold operating; rather, ramp it; if it cools too fast, it could crack the chips)
6) on Q315 PC rack, start 'remote operate detector' on each of 9 PCs
7) start cbass; good luck ...

Computers:

The five readout-computers have a rack of their own.  The rack carries a Keyboard/Video/Mouse selector at the top, a single video screen for all five, and a pull-out drawer (not shown) with keyboard and mouse.  At the right, one can see two pairs of orange fiber-optic cables coming into all but the bottom computer, and two ethernet cables coming into all five.  This arrangement allows the nine images to be readout in about 1 second in full-screen mode (72MB images).

The computers are running Windows NT.  Each is set up so the array of icons and available programs should be the same.

The individual detector modules are numbered as shown, viewing from the x-tal position.  Computer 0 handles modules 0/1, 1 handles 2/3, etc.  The last computer handles only one module.  The readout is handled by hardware and software from PixelVision.  Each electronic module has it's own number, in the range 3900 - 4300.  The correspondence between the module and the readout number is shown in the notebook, page 150.  A significant possible problem is that if the computers lose power and the detector does not (or is it the opposite?) the addresses from each computer to its respective module may get garbled.  We will install a UPS for this computer station to lower the possibility of problems.  This situation is fixed with program DBGLX32, which must be run on each of the five computers.  Here is roughly the protocol:

    1. Choose one module with the pushbutton.
    2. Open file C:/program files/pixelview3.21/statusframe&voltage_v2.cdb
    3. Push <run script>.
    4. This gives the ID number at the bottom of the scrolled window.  ADC0(0) is the output from the temperature controller.  It should be near zero for a quiescent cooler and ~20 if it's running.

In that directory one also can find the script FixModuleID.  Use that to fix it if necessary.  The detector power should be cycled after this to complete the fix.

To start up the temp. controller: first make sure that the detector-control APIs on w10 are not running.  Then one should close other windows and start up Operate Detector on each computer.  Then on the first computer, start one copy of Quantum Console.

    1. Select <connect to detector processes>
    2. Select <enable temp control>

The "set" command means "go to this temperature as fast as you can."  Don't do this to change the temp. by very much.  Typically, one would "set" to zero C to equalize all of the temperatures and get the Peltier system going.  Then one would select <ramp to operating temp> or whatever it is to get it cold.  Similarly there is a "ramp to 10 deg" or something like that for shutdown.

Program Pixel View can be used to find crude signs of life for each detector module.  More on that later -- maybe.  It's in the notebook.

Other files:  Computer 0 has directory D:/pv_sw/bin_903.  File detector_db.txt has a list of all the pixelvision readouts, computer names, etc.  Maybe this will need to be changed if computer names are changed.  File detector_env.txt has various environment-variable names used by the software.  File gains.txt has one gain value for each of the 36 chip quadrants.

Gains: The actual gain of the machine is about 2.5 ADUs for a 12keV photon.  A rather crude flood field (water rings are ok) with a few thousand ADUs in each pixel can be used to adjust the relative gains for each quadrant.  We'll get a protocol for doing this periodically.

Alignment Methods:  [This is a work in progress and wants some macros to do the work.]

The motorized table, the half slits, and the collimator aperture can be used for alignment of the diffractometer to the instrument.  The "lineup" routine in OptiX, which does pure horiz.and ver. motions is fine for aligning the beam-limiting aperture in the beam after the beam has been "max"ed.

We have devised a concise and seemingly pretty accurate scheme for optimizing the pitch/yaw of the diffractometer. At the end we were making height adjustments in the 60-100 micron range, that is, differentials from the front to the back of the table of 40 microns.  Realize that fine pitch and yaw adjustments have essentially nothing to do with maximizing the beam that comes through the collimator.  Instead, it assures that the beam coming out of the collimator will hit the specimen position.

1. Start with a beam from the optical system that has been slitted to about 0.5mm high and 0.8mm wide. Use "max" to center the hot part of the
beam in this area.

2. Put the 0.3mm aperture in the upstream end of the collimator, the 0.5 in the downstream end. Use "lineup" to center the diffractometer on the hot part of the beam.

We've worked out offsets for the Z1 and Z2/Z3 motors to pitch the table to move the upstream vertical halfslit by a known amount, holding the 0.3mm aperture still. We did the same for X1 and X2 to yaw the upstream horizontal half slit in the same way.  [Numbers to come.]

3. Adjust yaw:

• Measure the beam through the collimator.
• Close the horizontal halfslit (cbass command hfslit 1 1 -- see the notebook for a summary of the commands)
• Measure the beam through the collimator.
• Adjust the X1 and X2 motors according to the ratios described above to move the halfslit by 0.1mm then smaller increments to bring the collimator count to near half of the starting value.

5. Adjust pitch;

• Same sort of thing but with the vertical halfslit and Z1, Z2/Z3.  Command is hfslit 2 1

7. Adjust the slits just not to touch this 0.3mm beam.

8. Replace the 0.5/0.3 pinholes with the 0.3/0.2 ones.

By the way, lineup takes too long -- the increments should be twice as long in both directions and should go 2/3 as far.

We need a macro to do the pitch/yaw adjustment. The two measurements with the half slits closed can be scans according to the ratios above. At the
end of the scan the target value of the combined motion (XT) comes from linear interpolation against the two intensity values, n and n+1, that are
on either side of the half-height of the original full-beam count (YH = [full beam] / 2).  I think this is the correct equation:

XT = X(n) + (YH - Y(n)) * (X(n+1) - X(n)) / (Y(n+1) - Y(n))

Warning: This is an adjustment that should be very stable. When the beam position shifts for some reason, the pitch and yaw change negligible amounts. This is an adjustment that should be done no more frequently than every 4-6 weeks. For it to go bad, the motors on the lift table will have to miss steps. To track the sense of any changes will give a clue which motors are missing steps.

Composed by R.M. Sweet, 2-2-02