1. Recent development of the Supersonic Gas-Jet Beam profile monitor
Dr. Hao Zhang

2. Outline Motivation Experimental Setup Skimmer size and resolution
Jet distribution measurement

3. Motivation Diagnose the particle beam non-invasively
Preserve the vacuum more effectively
Better understand the gas-jet dynamics when using this monitor

4. Get-jet Monitor Setup

5. Generation of Supersonic Gas jet*Pb
For our case, P0 = 5 bar, Pb ~ 1.0e-3 mbar => xM/d = 1500; d =30mm=> xM = 45 mm *

6. Skimmers & MCP
V. Tzoganis, et al. IPAC2013

7. 2-dimentional profile imagingY X
V. Tzoganis, et al. IPAC2013

8. Resolution VS 3rd skimmer size
Beam size mm
sx (Gas jet)
0.42
0.56
sy (Gas jet)
1.23
0.53
sx (Residual Gas)
1.01
1.52
Skimmer size
7.2×1.8 mm2
4×0.4 mm2
Oriental angle
45˚
32˚

9. Smaller 3rd skimmer Skimmer size 4×0.4 mm2 Oriental angle 32˚
Beam size mm
sx (Gas jet)
0.56 ± 0.02
sy (Gas jet)
0.53 ± 0.03
sx (Residual Gas)
1.52 ± 0.07

10. Can we go even smaller?? Fresnel zone plate
Largest hole size is less than 2 micron for our case
Fresnel zone plate
Photon sieve,

11. Fresnel zone plate
Currently installed to replace the 3rd skimmer. But initial test shows no image from the micron jet.
Possible reason:
The gas is not fully monochromatic.
We might not get the focus in the electron beam region. The focus length f ~ 1/ λ ~ sqrt(m*T), so lower the gas temperature, lower the focus length. The supersonic gas molecule's temperature is unknown.
The density of the gas jet is too low to detect.

12. Resolution problem
Particle beam
Beam size 1
Beam size 2
Gas jet curtain
?! The gas curtain distribution will affect the resolution of this method. Having a method to know the pressure distribution of the system will help us understand the gas curtain distribution better.

13. Last update: Moveable Through Gauge module
Alignment is based on both the laser and gas-jet image, but the measured pressure curve is still due to the pressure raising of the chamber as a whole instead of the jet itself
New Moveable gauge chamber is added

14. Measurement from the previous through Gauge
Plot of the max-min pressure of the subtracted data VS the Gauge horizontal location

15. Newly installed compression gauge module
Slit
Compression Gauge Module
Gas jet curtain
Slit size
10.0 × 2.0 mm2

16. First meaningful result
The blue curve represent the case when partial of the jet enters the compression gauge module through the slit, while the purple one shows the case that there is no jet entering the slit and the pressure bump is from the overall pressure change due to the jet flowing into the first dump chamber

17. Vertical Scan

18. Gaussian fit
s (mm)
1.01

19. Automation for moveable Gauge Scan
Scope
Camera
Master Trigger PC
Pico-Current Meter
Pulse Generator
Relay
Pulse Valve
24V DC Voltage Supply
Moveable Gauge

20. Time Sequence Take photos (Matlab controlled software trigger)
Pulse valve open (Pulse generator)
Move gauge position by step motor(Matlab Controlled)
4.0 s delay
(pulse generator)
10.0 s delay
4.0 s delay
Scope start
(Matlab Controlled)
Pulse generated by Camera strobe
(Matlab Controlled)
Scope stop and transfer data
(Matlab Controlled)

21. 2D Scan
7.5 mm
About 32˚
6.0 mm

22. Mach Disc study Pb
For our case, P0 = 5 bar, Pb ~ 1.0e-3 mbar => xM/d = 1500; d =30mm=> xM = 45 mm
From

23. Gauge pressure VS Nozzle skimmer distance
This curve give a Mach disk about 25 mm, which is in the same order of magnitude with the calculation.

24. Conclusion and Future Work
Summary
By reducing the 3rd skimmer size, we improve the resolution of the jet image.
Developed a moveable compression gauge module to measure the jet distribution.
Automated the moveable gauge measurement process
Preliminary result of the jet distribution agree with the setup
Gas dynamics study about the Mach disk.

25. Any Questions?
Thank you