1. The Cockcroft Institute generic Xband stretched wire system

2. Overview of talk  Basic review of previous Daresbury (DL) stretched wire setups  Introduction to the proposed Cockcroft (CI) Xband stretched wire setup  Overview of the Network analyser system setup  Overview of the automated wire control system setup  Overview of optional extras to the setup

3. Previous Daresbury Stretched wire systems

4. DL FP420 stretched wire setup Schematics courtesy of: Ian Burrows Clive Hill

5. DL ILC crab cavity stretched wire setup Schematics courtesy of: Ian Burrows Clive Hill

6. Proposed Cockcroft Institute generic Xband stretched wire setup

7. CI XBand Stretch wire high accuracy piezo-actuators We a proposing a new Cockcroft stretched wire system aimed at analysing the transverse HOM’s of a device under test (DUT) typically in the Xband frequency range.  The proposed Xband stretchwire setup will be:  Fully automated (for reproducible results and quick setup time for generic cavities)  Be accurate on a nanometre scale  Vertical to avoid wire sagging  High bandwidth range  It will be a modular and portable design  These aspects will make it far more accurate that the previous CI stretchwire setup

9. Stretched wire Network analyser system

10.  Given the restraints of the CI budget the Aligent 5320C-525 2 port network analyser is the best option that I have found so far for the purposes of an Xband stretched wire setup.  It is a 2port Network analyser to goes up to 40GHz  For an Xband structure the third dipole band is typically below 40GHz – so this scope is sufficient to analyse the HOM’s in such a cavity.  Special 2.4mm SMA cables would have to be used – (standard SMA cables only go up to 18GHz). It would be advisable to have these cables phase matched to prevent erroneous errors produced from temperature fluctuations.  An electronic calibration kit would be required for standard calibration purposes of calibrating from the ports of the network analyser to the DUT.  This unit is controllable over a GPIB link and is compatible with MATLAB The Aligent 5320C-525 Network analyser

11. Description Model NumberCompany Part baseline costFeatures Total Cost of Part Network analyser system Network anayser N5230C- 420Aligent UK 2 port S parameter Only 10MHz to 40GHz - 25% academic discount Academic discount 25% - Could also use the existing ASTEC scope Calibration kitN4693AAligent UK Electronic calibration kit 10MHz to 50GHz, 2 port kit. Faster and more accurate than the mechanical kit - 25% academic discount Academic discount 25% - Could use ASTEC manual calibration kit 40GHz cables85133F1Aligent UK Typical off the shelf cables are only good for 18GHz - we need cables up to 40GHz- this is a set of 2.4mm SMA (1x((f)to(f)) and 1x((f)to(m))) - Phase matched - 25% cables good to 50GHz - 25% academic discount Academic discount 25% Vertical Test standDL A machined vertical test stand for the stretch wire rig Mountings for stretch wireDLMountings for the stretchwire WireInesto UK Wire for Xband stretchwire rig: obtained from INSETO UK: Bonding wire in Cu, Al or Au 18um to 500um. We will require 50m of wire within this range - Note the wire has a shelf life Positioning systemDLWire insertion device Network analyser system setup

12. Stretched wire Network analyser questions:  At the moment the present CI stretched wire design does not include launch cones… this will cause a problem with mode conversion (i.e. instead of a launch cone a step transition will be used and a long beam pipe to kill of evanescent modes – so will have to operate below cut-off). Would you instead insist on launch cones – because although this option will prevent mode conversion, it will not make the setup generic i.e. new flanges and launch cones will be required for each structure (which will be very expensive).  I have gone with the option of using phase matched cables to prevent erroneous errors from temperature changes – would you recommend the use of such cables?  The wire that I have sourced for the stretched wire setup is “bond wire” as such it generally has a limited shelf life of 1year before it oxides – would you use such wire (in the case of Al the oxidation is of little concern  The wire I have sourced ranges from 18um to 500um, generally the smaller the diameter of the wire the less the perturbation of the fundamental band. What diameter would you recommend (due to resistance limiations)?  The wire will have to be soldered to the 2.4mm SMA connections – what material would you recommend for the wire Cu, Au, Fe, Al?  If the stretched wire is to be used as a precursor to a beam test on a “clean” cavity, then should the stretched wire system not also include an insertion mechanism? What servo system would you recommend?

13. Stretched wire control system

14. CI XBand Stretch wire high accuracy piezo-actuators  There are several companies that specialise in high precision peizo-actuators: Physics instrumete, New Focus and Newport Physics to name a few..  So far the best peizo actuator for the purposes of an Xband stretch wire rig that I have found in terms of price and range is from Newport Physics - the PZA12  It has the following features  Nanometre precision – 0.03um steps (for Xband we need at least micron precision)  12.5mm travel  2mm/s maximum travel speed  We will need 4 of these actuators two sets to control the position of both the x and y of the stretched wire  If we use a PZC200 switchbox we can control up to 8 of these units

15. DescriptionModel NumberCompanyPart baseline costFeatures Total Cost of Part Nanometer precision wire Positioning system PZA12 actuators x 4PZA12Newport corporationx and y wire steers PZC200 switchbox kit includes cables PZC200, 15769- 02, 41791-01Newport corporationcontrol unit for steers Manual piezo actuator controllerPZC200Newport corporation manual control unit for piezo actuators Power supply for piezo actuatorsNSC-PS25Newport corporation power supply for piezo actuators RS485 cableNSC-CB3Newport corporation3m cable to controller RS485 cableNSC-CB2Newport corporation2m cable to computer RS232 to RS485 converterNSC-485-232-INewport corporation Cable converter from switchbox to computer RS232 terminal - allow a compter to drive the switchbox components PZA12 control system setup

16.  The stretched wire piezo-actuator systems will look like this  Four PZA12 actuators controlled via a PZC200 switchbox using either a computer or via the manual PZC200 controller  The PZC200 can be controlled via a C programming language, and is MATLAB compatible in that sense.  Backup manual system to individually move the piezo actuators.  Control system setup is modular and portable. If a larger range of transverse wire motion greater than 12.5mm is required for an RF structure then the control system can be modified and or swapped out. PZA12 control system setup

17. Description Model NumberCompanyPart baseline costFeatures Total Cost of Part Computer control system SoftwareMathworks Matlab - perpetual single licence (£375). Instrument toolbox (£150). Data acqusition toolbox (£150) Perpetual licence to acquire and automate the experimental system. Cheaper than yearly Labview cost (£2722). Matlab will be used to drive both the Network analyser and the Piezo actuator steers. Out-sourced to UMAN? Computer STFC RAL Standard - Optiplex 780 SF (no monitor)DLComputer to control setup Out-sourced to UMAN? PZA12 control system setup computer and software  The entire system will be automated  The software of choice will be MATLAB, based on two factors:  1) Cost – MATLAB is considerably cheaper for a perpetual license than other commercially available systems  2) Both the Network analyser and the Piezo-actuators are Matlab compatible. EPICS or similar free control software could be used to create a user friendly GUI, but the MATLAB compatibility greatly negates this and the amount of raw programming required for the setup.  This is in addition to the pre-supplied software of these devices.

18. PZA12 control system setup questions:  The present control system design is modular, but due to the choice of the PZA12 peizo- actuator it is limited to a maximum transverse motion of 12.5mm. For the purposes of looking at LHC collimators or other RF devices, what maximum range would you be interested in i.e. what range and tolerance are you interested in?  The current control system has a backup manual system as part of the design. A second manual (mechanical system) could be added as a final failsafe (although less accurate) as either a spare set of flanges or as part of the current design – is this advisable or do you consider it as over design?

19. Optional extras to the setup

20. Description Model NumberCompanyPart baseline costFeatures Total Cost of Part Optional extras Piezo-strian gauge and tensioning systemNPA25SGNewport corporation Strain gauge - up to 150N pull Optional extras PZA12 actuatorPZA12Newport corporation Wire tensioning system - use piezo actuator as a stepper motor to tension the wire utilising the PZC200 switchbox Control unit for Strain gaugeNPC3SGNewport corporation Controll unit for NPA25SG  A piezo strain gauge system has been included as an optional extra to the stretched wire setup.  This will allow the wire to be tensioned as part of the automation process, using a spare PZA12 actuator and the PZC200 switchbox.  Some Xband setups have included strain gauges in the past. This optional extra will allow the wire to be tensioned equivalently for each setup Optional extras to the setup

21. Impulse Forming Networks (IFN) produce an impulse from a step function or pulse and create a monocycle from an impulse.  A drawback to current stretched wire setup is that very short bunch lengths cannot be simulated using the present network analyser.  One option would be to use a signal generator and an impulse forming network. Pulses as short as 3ps could be generated in this manner.  This would greatly increase the cost of the setup and would only be of interest if the DUT was designed for an environment where this would be a factor. An entirely new set of equipment would be required for this option i.e. IFN, Pulse generator and a Scope…. Very short bunch simulation option – a thought?

22. Optional extra strain gauge system questions:  This item has been budgeted as part of the setup; should it be neglected or modified?  If it is included in the final setup, a semi empirical method would initially be employed to tension a given fixed diameter wire of a set material (i.e. Al, Cu, Au etc….) – comments thoughts?