1. HF Source Drivers Performance Observations and Recommendations Paul Debbins University of Iowa Nov. 10, 2004

2. Outline of Slides Electric Driver System –Wire Behavior Observations Recommendations –Reel Mechanics Observations Recommendations –Indexing System Observations Recommendations –General Recommendations Air Driver Systems

3. Electric Driver Wire Behavior - Observations Lack of wire constraint inside reel at longer extensions allows sufficient room for wire to become permanently deformed and kinked. This behavior establishes the force limit which can be exerted upon the wire without damage, this limit may currently be insufficient per CMS expectations. Wire kinks catch on spring fingers and contribute to wire drag inside detector pathways. Wire has escaped out bottom plate via constraining spring finger entrance holes. The wire was able to push the finger out of the way and escape through the bottom plate. Wire end set screw, which secures end of wire to reel, slips and can release, resulting in misalignment of source with garage and loss of control of wire.

4. Electric Driver Wire Behavior - Recommendations Clearly establish a wire force limit which prevents permanent kinking over extended use. Drivers have a force limit mechanism. Shore up current spring finger system to prevent wire escape. 1. Limit travel of fingers to prevent wire pushing through 2. Reduce entrance hole size Investigate methods to improve wire constraint over the current spring finger method. For example, an intermediate member between spring fingers and the source wire may distribute force and provide superior constraint performance, increasing wire force limits. Use a plate to pinch wire against reel edge rather than the set screw currently used.

5. Electric Driver Reel Mechanics – Observations Reel is currently mounted via a bushing and non-captive screw, which can come loose. Reel preload is established by a stack of several washers and shims which must be individually established for each driver. Reel friction and the potential for the wire to escape from under the disk are critically dependent on this adjustment. Reel rubs against base plate, which results in abrasion to the reel and buildup of a plastic “gum”. This increases friction between the reel and base plate. A plastic pad between the reel and base plate is not secure and can shift and jam. Reel end-stop mechanism is loosely constrained and reliable operation is not assured in different orientations of the driver, which results in false interruption of wire movement.

6. Electric Driver Reel Mechanics – Recommendations Reel should be mounted with captive hardware which allows precise setting of preload without shims. Reel disk should ride on bearings, which will eliminate the gum from reel galling, and establish a rigid and precise relationship of the reel to the base plate. The current plastic pad between reel and base plate should be secured with a screw or pin to prevent shifting and jamming. The reel end stop mechanism should be modified to be self centering to prevent false activation of the limit switches in all orientations.

7. Electric Driver Indexing System – Observations Indexing System appears generally sound Driveline of indexer has 7 rotary couplings, only 2 are needed for adjustment of system. Couplings are held by simple set screws and each coupling is a potential source of slippage which has been observed in operation. Indexing System – Recommendations All couplings other than the required adjustment points should be made rigid. The 2 couples for adjustment could be improved to provide more secure connections and improve adjustability than the existing set screws.

8. Electric Drivers General Recommendations Each driver is a “one of a kind”. Drivers are constructed with variations in their components which are not interchangeable. Consistency in the components and set-up of the drivers will improve maintainability and allow easy replacement of components. Drivers should be made identically. The drivers have many components that need relatively precise adjustment, and specific setup procedures. Well documented procedures would greatly Improve overall consistency and reliability of driver operation. Periodic maintenance procedures should be established. Comprehensive part manuals, part sources, spare parts, and tool kits would improve on site maintainability by any competent technician. Part and tool availability are important as the drivers are made of SAE components, yet reside in a metric country.

9. Electric Drivers Additional Recommendations A wire/source storage system should be developed which allows easy installation, removal and storage of the source. This would minimize radiation exposure during maintenance and setup, and help protect the wires from dirt and accidental damage. A vacant indexer channel or quick disconnect coupler should be provided for this purpose. Making all source wires be of identical length and clearly marked with a reference point would improve the wire installation procedure, and allow easy exchange of wires between drivers. The indexer plate should be separable so that a reel unit can be interchanged without having to deal with the several hundred individual connections between the indexer and the detector. The only modification necessary to accomplish this is to install an electrical connector for the switches on the indexer.

10. Air Drivers The air driver systems employ the same reel system so recommendations are the same as the electric systems. The indexing system is quite different and needs to be tested to evaluate its performance. The air drivers examined were not in operational order so their operation could not be evaluated. Extensive operation and testing with a dummy wire should be done to identify any potential bugs before real sources are used. Lifting equipment might be desirable for the air drivers since the source garage is located where one is likely to hold the driver during installation.