SNO Calibration System The SNO calibration source was designed to deploy sources into both the AV and light water volume between the AV and PSUP

All sources deployed on a manipulator system from a “URM” (Umbilical Retrieval Mechanism). They can be deployed either as “single axis” or “polyaxis”. Single Axis: Deployed sources vertically down from the URM. This allowed deployment either inside the AV or down guide tubes into the light water volume. Polyaxis: Deploy source with URM but attach side ropes that allow moving the source off the vertical axis once inside the D2O volume.

The URM contains both a rope to support the source and an umbilical that provides services to the source. Shown in the figure is a prototype of the URM showing the rope system (above) and the set of pullies used to store the umbilical. Both rope and umbilical are driven with stepper motors. The rope has a load cell to measure rope tension (load) and a shaft encoder to measure the length of the rope. The umbilical also has a haft encoder and loadcell. Umbilical Retrieval Mechanism (URM)‏ Prototype URM Mark I URM Calibration Guide Tube

Prototype URM Load Cell Stepper Motor Rope Winding Drum Shaft Encoder would go here but not on this unit Sliding Pully Block Umbilical Driving Wheel Load Cell Source Shaft encoder would go here. Load Cell

Services to the source are provided through custom made umbilicals. The umbilicals followed a standard design although the details would differ if a custom source was required. There would be a central tube or large cable around which a set of wires including an RG174 coax with it's plastic jacket stripped off. This assembly would be inserted into a silicone tube and then the space between central jacket would be potted with silicone rubber. Nominal diameter of the finished umbilical was 1/2”. Some special umbilical(s) were made with diameter 5/8”. This latter umbilical required a refitted URM with pullies sized to the larger umbilical. The reason for spiral winding the wires in the umbilical was because if they were not they would fail when being worked over the pullies. Different Umbilicals had different services. For instance the N16 source required a gas feed and return, a low V power supply and an coax single from a tag PMT. The laser umbilical used a 1/4” tube through which a fibre optic bundle was fed. Umbilicals N16 Umbilical Laser Umbilical Coaxial gas lines Fibre optic bundle

Sources are deployed into AV (D2O) volume through the “Universal Interface”. The UI had a glovebox on top of it to which the source URMs are attached. The sources are contained in a “source tube” below the URM. The system allowed a complete radon seal and light seal meaning the source could be deployed with the detector on. A gate valve isolated the URM from the detector volume. Universal Interface Source Tube Gate Valve URM Glove Box

Sources used a standard mount off the rope and umbilical. The rope and umbilical are attached to a carriage which attaches to a weight (for negative buoyancy) and the source attaches to the bottom of the weight. The umbilical was along the centre line. The rope was attached off centre on a rotating collar that was required to prevent the rope and umbilical from twisting around each other. This rotating carriage was an add on to the original design and found to be essential. The carriage also had pullies to attach side ropes to. Source Mounting N16 Source Rope Umbilical Rotating Collar Side Rope Pullies Pivot Weight Carriage

The control system was a client/server system with the server running on a DOS PC called MANIP. The client connected by TCP/IP. There was a client GUI in the SHARC DAQ control system and a stand alone GUI program written in TCL that ran on many unix systems and allowed control from off site. The control hardware was mostly custom boards. There was a watchdog timer circuit that would stop the system if the computer stopped working (necessary since the stepper motors could potentially continue to work without computer control). The software allowed different sources and ropes (such as the side ropes) to be connected dynamically and the control software would compensate as appropriate. The rope and umbilical were “different axes” in the jargon of the control system. But the source is “driven” as a combined system. Control System

MANMON Display showing the source in single axis mode.

Bumper to make it easier to deploy calibration sources down guide tubes

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