# Presentation: 836517

## RF, DAQ, and Instrumentation Requirements for the ILC Vertical Cavity Test Stand at IB1 (ILCTA_IB1_VTS)

- _Basic Requirements for Vertical Cavity Testing:_
- Provide stable RF power to the cavity, with control of amplitude, phase, and frequency
- Measure incident, reflected, and transmitted power of the cavity (including transmitted power from HOM couplers)
- Provide interlocks for both personnel and system safety
- Provide automated data acquisition and control (reproducibility)

- J. Ozelis

## Our Approach :

- _Our Approach :_
- System to be used for PRODUCTION cavity tests, as part of the cavity process development program. We are interested in understanding and quantifying cavity performance, over the course of many years, and many tests. This means system must satisfy the four R’s:
- Robust, Reliable, Reproducible Results,
- This is not an RF system development project. The object of the exercise is to test cavities, not develop control systems.

- Therefore the system should be based on established technology/designs and use off-the-shelf components as much as possible.
_**Our Solution :**_
**Replicate the production cavity vertical test system in use at JLab, w/ appropriate modifications/improvements for 1.3GHz operation.**

- J. Ozelis

## Specifications/Features of the RF system - general

- _Specifications/Features of the RF system - general_
- Adjustable frequency range 1.2-1.4 GHz, using coarse and fine manual adjustment – allows investigation of other than  mode, cavity frequency differences due to BCP amounts, manuf. tolerances, temperature, etc.
- Frequency stability of ~1Hz.
- Adjustable phase range of 360°.
- Maximum amplifier output of 500W at 1.3GHz.
- Maximum loss between amplifier and cavity ~ 3dB.
- Amplitude adjustment of RF output to provide ~1-35MV/m when cavity nearly critically coupled (.5    2).
- Switchable between 500W and 1W (built-in) amplifier  - for cable calibration, Q0 vs T measurements, coupling determination, etc.
- High power SPDT switch to divert RF to 500W load when interlock fault condition detected.

- J. Ozelis

## Specifications/Features of the High Power RF system

- _Specifications/Features of the High Power RF system_
- High power amplifier -  500W, 1270-1310 MHz  (OPHIR RF).
- Dual directional couplers  - 30dB directivity @ 1.3GHz (Narda).
- RF load  - capable of 500W CW (Microwave Devices).
- SPDT switch - 500W, 80dB isolation, 0.2dB max insertion loss (Narda).
- High power circulator - 500W, 1.1-1.4 GHz BW, (UTE Microwave).
- Cables/connectors – 1⁄2” Heliac w/ “N” connectors, except inside Dewar; SiO2 insulated SS hermetically jacketed cables in Dewar (Meggitt Systems).
- 	**→ ** breakdown potential at connectors, even using Meggitt cable?
- 	**∴** JLab to test He pressurized (> triple point) jacketed 	   cable
- AC power – 208V/3 , connected to interlock system.

- J. Ozelis

## Specifications/Features for the LLRF system

- _Specifications/Features for the LLRF system_
- Based upon VCO/PLL design.
- External RF source used as VCO (Agilent E4422B).
- Coarse and Fine frequency adjustment via 10-turn pots.
- Manual phase shifter (190° phase shift at 1.3GHz, Narda 3752).
- Vector Modulator for amplitude/phase control (GT Microwave Model SA-39-AR or similar).
- Adjustable loop gain (variable gain amplifier) prevents oscillation over wide dynamic range.
- Crystal (diode) detectors for observing signals, atten. adjustment (Omni Spectra 2086, Agilent 8472).
- PIN switch to control RF on/off during decay measurements or pulsed RF processing (American Microwave 2184).

- J. Ozelis

## Slide 6

- J. Ozelis

## The transmitted power network has a switchable LNA and variable attenuator, both can be controlled by the computer.

- The 6 dB pad before the LNA ensures that there is a minimal gap in the continuous gain control settings.  Without it there would have been a 12 dB dead band.
- The phase shift associated with the PIN attenuator was measured and included as a lookup table in the program.  The compensation values are factored into the vector modulator algorithm.
- Circulators are used to reduce the mismatch and ensure more stable power meter calibrations.  The 10 dB attenuators used in the incident and reflected power path also serve that purpose
- Only low drift fixed devices are used between the power meters and the cavities to ensure calibration stability/validity.** **

- J. Ozelis

## The VCO is located externally.  This allows the use of stand-alone commercial RF sources as VCOs. 

- The VCO is located externally.  This allows the use of stand-alone commercial RF sources as VCOs.
- The 50 dB attenuator may be necessary due to the excessive tuning sensitivity of the VCO, which is 5.6 MHz/V.
- Crystal detector gain set to reduce the square law errors while maintaining a 1V amplitude at the DAQ input.
- Manual phase shifter in addition to VM, used for initial tuning, “finding” cavity.
- Computer controlled vector modulator is used for amplitude and phase control.
- All crystal detector signals are buffered and available for observation using an oscilloscope.
- Computer controlled and automatic data acquisition ensures repeatable data and methods independent of operator.

- J. Ozelis

## Specifications/Features of the DAQ HW & Instrumentation

- _Specifications/Features of the DAQ HW & Instrumentation_
- Power meters for measurement of Pi, Pr, Pt, and HOM power (Agilent 4418B/4419B, w/ 8482A sensor heads).
- Frequency counter to measure cavity frequency (Agilent 53132A) .
- Oscilloscope w/ “Roll” feature to allow observation of cavity signals in RT (Textronix TDS3024B).
- Dewar pressure transducers (MKS Baratron), thermometry (Lakeshore Cernox w/ Model 218 monitor) & , and LHe level sensor (AMI Model 135-2 & sensors).
- Radiation detectors (ion chambers) – RadCon supplied or ? Also part of interlocks/safety system.

- J. Ozelis

## Transmitted power network module

- Basic system components and DAQ PC

- J. Ozelis

## Specifications/Features of the DAQ SW

- _Specifications/Features of the DAQ SW_
- DAQ SW available from JLab
- SW is written in LabView environment, and provides :
- Automatic Pt decay measurement
- Automatic calculation of 
- Interactive cable calibration routine
- CW display of E, Q0, Rad
- Online display of Pi, Pr, Pt, and correction factors
- RF output power control
- Phase control/optimization
- Display of cryogenic status (LHe level, temps, dewar pressure(s))
- Calculation of Q0, Qext fp, Qext in, Qext HOM1, Qext HOM2, Eacc
- Logging of all data
- Graphic display of Q0 vs Eacc
- Graphic display of Rad vs time, Rad vs Eacc

- J. Ozelis

## Slide 12

- J. Ozelis

## Status – where are we

- _Status – where are we_
- Developing instrumentation, equipment, and component list – 50-60% complete. Can place orders when assured of $$ availability (after cryostat design is finalized, RFQ issued, and quotes received).
- 2 amplifiers (500W) ordered, one for JLab, one for FNAL.
- Beginning to assemble documentation/schematics in preparation for design finalization.
- LV SW downloaded to FNAL.
- Rack and cabling layouts begun.
- Coordinating efforts w/ similar program of modifications to JLab 805MHz system (**→ **1.3GHz).

- J. Ozelis

## (- $30,000 (Amp))

- J. Ozelis

## Slide 15

- J. Ozelis

## Slide 16

- J. Ozelis

## Status – where are we

- _Status – where are we_
- Developing instrumentation, equipment, and component list – 50-60% complete. Can place orders when assured of $$ availability (after cryostat design is finalized, RFQ issued, and quotes received).
- 2 amplifiers (500W) ordered, one for JLab, one for FNAL.
- Beginning to assemble documentation/schematics in preparation for design finalization.
- LV SW downloaded to FNAL.
- Rack and cabling layouts begun.
- Coordinating efforts w/ similar program of modifications to JLab 805MHz system (**→ **1.3GHz).

- J. Ozelis

## Plan – where we are headed/open issues

- _Plan – where we are headed/open issues_
- Continue information transfer re: schematics, etc. Trips to JLab planned for ILC EP cavity testing later in summer, perhaps trip earlier to collaborate on RF system design.
- Finalize design, subject to review.
- Begin involvement w/ AD Interlocks and Rad Safety Groups re: interlock system design, fabrication, etc. This must be integrated with the RF system at an early stage. Need to determine type/availability of radiation detectors (needed for DAQ as well as Safety System).
- Finalize and prioritize equipment lists, M&S budget, begin procurement of FY06 items.
- Prepare more formal (MPP) project plan.

- J. Ozelis