SHARC II Installation Guide


Installation Topics:

relay optics preparation 
cryostat installation 
electronics installation 
power-up check

Relay Optics Preparation (only if SHARC2 is on the Cass focus)

SHARC II goes on the right port of the relay optics.  Before installing the cryostat, verify that the right rotator is functional with the UIP "ROTATOR /RIGHT" command.  If it has not been homed since installing the relay optics, do so, using the instructions on the main CSO web page.  Finally, set the rotator in position for the cryostat installation:  "ROTATOR /RIGHT 0".

OPTIONAL optical alignment:  Using the Hertz mounting plate and the acrylic screen, it is possible to adjust the relay optics mirrors so that the beam from the secondary mirror lands on the rotation axis of SHARC II.  As a first step, turn the bottom "turntable" mirror M3 full counterclockwise.  Next, install the Hertz mounting plate (which has rectangular standoffs) on the rotator.  The acrylic screen goes on top of that.  With the optical path clear, and with the dome open part way, a silhouette image of the secondary mirror should form on the screen.  Adjust the rotation of M3 and tilt of the ellipsoidal mirror (M5) to center the silhouette in the circle on the screen.  One should also verify that the circle is centered on the rotation axis by spinning the rotator.  If not, reposition the screen.

In any case, the 3 relay optics mirrors feeding SHARC II should be rigidly positioned.  Some of the screws have a tendency to become loose over time.

***NOTE*** In 05A we commissioned a new Nasmyth platform on which SHARC-II will be permanently mounted.

Cryostat Installation

The black mounting plate on the under side of SHARC II is integral to the cryostat;  the cryostat goes directly on the rotator without any additional interface.  SHARC II is normally lifted with eyebolts on the top ring.  Please run an additional strap as a safety against failure of the eyebolts and/or top ring.

SHARC II attaches to the rotator with 8 each 1/4"-20x1" screws.  The precise alignment of the tapped holes in the black mounting plate with the thru holes in the rotator is a little difficult since they cannot be viewed easily.  A solution is to thread one or two tapered alignment pins into the holes in the mounting plate.  The alignment pins should be unthreaded and replaced with screws at the end of the installation.

The base of SHARC II is numbered to match the labels on the rotator.  With the rotator at 0 degrees, the helium fill tube of SHARC II should be at the back (away from control room), and the filter wheel in front (toward the control room).

Electronics Installation

ESD GUIDELINE:  Please wear ESD wrist strap to cryostat when connecting or disconnecting RFI boxes, amplifiers, and thermometry enclosures.

List of required components:
  1. 12 amplifiers (numbered 1-12), with attached multiplexers, which get connected to RFI boxes 1-12
  2. 1 thermometry enclosure (#13; green markings), which gets connected to RFI box 13
  3. A/D unit (12U height), on bottom of rack
  4. Analog electronics control chassis (6U height), next up on rack
  5. Multiplexer buffer, between analog electronics control chassis and shelf
  6. Motherboard diode to A/D interface, next to multiplexer buffer
  7. Neocera temperature controller, attached to top shelf with electrically-isolating bracket


ESD GUIDELINE:  Please use caution to prevent electrostatic discharge when connecting cables to SHARC II and electronics.

List of required cables:
  1. 12 amplifier-to-A/D cables:  37-pin D's, straight through, molded gray, very flexible; bottom of amplifier (multiplexer) to A/D unit; should be arranged to accomodate full rotation of cryostat (+-90 degrees from installation configuration)
  2. 12 amplifier power cables:  custom light gray cables with right angle connectors; right-angle connector on side of amplifier, straight connector on analog electronics control chassis; should be arranged to accomodate full rotation of cryostat
  3. 2 BNC cables from analog control electronics chassis to A/D unit:  one connecting 1 kHz = bias reference, other connecting 256 kHz = demodulation reference
  4. AC power for multiplexer buffer
  5. Multiplexer buffer input signal from analog control electronics chassis (6-pin LEMO) to multiplexer buffer (9-pin D)
  6. Multiplexer buffer output signal from multiplexer buffer (9-pin D) to sharcii computer:  straight through shielded circular cable
  7. Multiplexer signal from multiplexer buffer (9-pin D) to multiplexer daisy-chain (9-pin D), which begins on the underside of an amplifier (multiplexer) in the front:  long (perhaps double) ribbon cable which accomodates full rotation of cryostat
  8. Multiplexer signal daisy chain:  11 ribbon cables with 9-pin D connectors which interconnect undersides of amplifiers (multiplexers)
  9. Programming cable:  long cable from analog control electronics unit (Centronics connector) to sharcii computer (IDC connector, port C)
  10. AC power for Neocera temperature controller
  11. Thermometry cable:  connects thermometry enclosure connector "X" (37-pin D) to 4 connectors on back of Neocera; one dangling 15-pin connector unused
  12. Neocera serial cable:  connects Neocera serial port to sharcii computer serial port; 9-pin D, straight through
  13. Amplifier power:  connects power controller to analog electronics control chassis; 9-pin D connector
  14. A/D power:  connects power controller to A/D unit; 2 separate cables with circular connectors, plus ground wire with banana plug which connects to analog electronics control chassis
  15. 8 fiber optic cables (orange):  connect A/D unit to sharcii computer
  16. Motherboard diode interface box to A/D unit "row 13":  37-pin D, straight through
  17. OPTIONAL:  Motherboard diode interface box to analog electronics control chassis:  12 each 9-pin micro-D connectors
  18. Motherboard diode interface box "BNC1" to chopper monitor (in sidecab):  long BNC cable; should put ~900 ohm resistor in series to dampen ringing

Power-Up Check

The CSO staff should ideally perform these checks instead of the first-night astronomers:

AMPLIFIER BATTERY:  It is very worthwhile to check the battery voltages (approx. +15 V, -15 V, ground) at the SHARC II end of the cable before plugging it in.  Also, it is very worthwhile to check that none of the conductors are shorted to the telescope.  The analog electronics has only limited protection against problems in the battery voltages.  After these checks, the power-up sequence is the same as performed every evening ("Powering Up the Electronics").  After the power up test, disconnect power until the instrument is started up in the evening.

A/D POWER SUPPLY:  The voltage settings are +6.0V and -7.0V, and the currents should be in the neighborhood of  +2.7A and -2.2A when the cables are connected to the A/D unit.  This power supply stays on all the time.

NEOCERA TEMPERATURE CONTROLLER:  Getting two reasonable, updating temperatures is a necessary (but not sufficient) condition for verifying that the 3He cycle can be carried out.  The Neocera stays on all of the time.

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