# Presentation: 349889

## Comparison of Microwave and Mechanical Measurements of  FXA-001 Structure.

*Tug Arkan, Harry  Carter, Dave Finley, Ivan Gonin, Temir Khabibouline, *
*Gregg Kobliska, Gennady Romanov, *_***Nikolay Solyak***_***,**** Ding Sun, Evgeni Borissov.*

-  FXA-001 Structure
- Single cell measurements
- Mechanical measurements
- Setup for bead-pull measurements
- Plunger and bead-pull measurements
- Tuning of FXA-001
- Summary

## FXA-001 Structure.

**We have our first X-Band structure**.

**It is the first X-band (11.424 GHz) RF structure built, measured and tuned  at FNAL.**
** **
**It is tapered structure about 20 cm long, made of  20+3 cells.**
**It is named FXA-001.**
**Note the cells, couplers, rf flanges, water pipes, beam tubes.**
**It took a little more than nine months.**

## Cell and coupler production.

**	****	****	****	**

-   FXA-001 is made according to SLAC’s design of T20VG5 for NLC High Gradient Testing.** **
-  45 mm RF disks were fabricated by two different vendors LaVezzi Inc. (3 sets) and Medco  Inc. (2 sets).
-   An outside vendor fabricated the Input and Output RF Couplers. Contour Manufacturing and Metrology Inc. (CMM) is a diamond turning ultra precision machine shop and it is located at Troy, MI.

## FXA-001 Disk Specifications

-   Cell dimensions: 2a, 2b, t (iris thickness), D (cell length) and R=t/2 (round ris).

- D=8.74268mm

- Nominal Frequency = 11.417 GHz

## RF measurements for LaVezzi and MedCo disks 

*	**LaVezzi disks**	**	**	**	**MedCo disks*

## 2a, 2b deviations for LaVezzi and MedCo disks 

*	**	**	**	**	*

*For ****MedCo****** ****discs the random scattering of frequencies were found to be rather small, but some systematic error for “0”-like mode of approximately 20 MHz exists in both sets. *
*    **To evaluate which dimension is responsible for this systematic error a linear approximation of the set-up frequencies has been used. Assuming that the errors ****a, ****b are small, the frequency shifts for both modes can be expressed as*

*Frequency derivations are well known from cal- culation. So,errors ****a and ****b can be found. *
***LaVezzi**** discs have smaller systematic errors and bigger random errors. But working frequency higher than 11.424 GHz*

## Errors in  bead pull measurements 

*   **Wave, reflecting from cell vs. cell number at 11.400 GHz*

*Error in frequency measurement for FXA-001 is  about **** 0.6 MHz*

## Mechanical measurements

**Cordax Coordinate Measuring Machine in QC Laboratory**

**OGP Optical CMM**

## Iris Profile Measurements

- Vendor #1 (LaVezzi) looks “good” here.
- ... but would not pass single disk RF QC due to large disk to disk variations.

- Vendor #2 (MedCo) looks “not good” here.
- ... but single disk RF QC showed very good disk to disk control.

## Frequency Calculation with MedCo real Iris Profile

-  Freq. nominal = 11.417 GHz       	actual = 11.394 GHz

## Frequency Calculation with MedCo iris Profile

## RF measurements on FXA-001

- Bead pull setup in RF Factory Clean Room A

**Network analyzer.**
**Bead pull support.**
**Pulley.**
**Data acquisition and data analysis is controlled by computer.**

## RF Measurements on FXA-001(G.Romanov, D.Sun, I.Gonin, T.Khabiboulline)

- Bead Pull Principle

-  A network analyzer puts an rf wave into the structure composed of cells and couplers.  Some of the wave is transmitted, some is reflected, and the reflected power measured and analyzed.
-  A metal “bead” (shown as “needle” in the figure) is pulled along the length of the structure and disturbs the rf wave.
-  The analysis yields the amplitude and phase of the wave.

- From PAC95 paper on DESY S-Band setup

- RF Measurements on FXA-001(G.Romanov, D.Sun, I.Gonin, T.Khabiboulline)

## RF measurements on FXA-001 (1)

- Im vs. Re part of reflected rf wave at 11.400 GHz before tuning.

-  The bead is pulled through the structure at a constant speed over about 140 seconds.
-  Data is taken at constant time intervals.
-  The data taking window is about 10 msec.

-     Note: You want 11.424 GHz; thus the cells are about 24 MHz low.

## RF measurements on FXA-001 (2)

- Amplitude of reflected rf wave at 11.400 GHz before tuning as a function of time.

-  You want this to be flat -  which it isn’t.
-  This is the same measurement as the previous slide but it is easier to see that every third peak is smaller than the other two.

## Tuning of FXA-001

**Tuning of FXA-001 structure**

## RF measurements on FXA-001

-           Amplitude vs. time after coupler tuning at 11.422 GHz.

## Summary

- First Accelerating Structure FXA-001 was built, measured and tuned at FNAL
- Built RF setups for low-power RF measurements.                       (RF Factory).
- Mechanical and RF QC of discs discovered noticeable errors in disk dimensions, made by vendors.  This errors will be fixed in next structures.
-  Automation of RF measurements. Data acquisition and data analyzing is controlled by computer.
- FXA-001 structure was measured and tuned to working frequency 11.424 GHz.