Difference between revisions of "Emittance Test"
| Line 298: | Line 298: | ||
<math>r = \frac{(1.6 \times 10^{-19} \mbox{C}) \times ( 5 \times 10^{-5}\frac{\mbox{kg}}{\mbox{C} \cdot \mbox{s}})}{mv}</math> | <math>r = \frac{(1.6 \times 10^{-19} \mbox{C}) \times ( 5 \times 10^{-5}\frac{\mbox{kg}}{\mbox{C} \cdot \mbox{s}})}{mv}</math> | ||
| − | <math>mv = P = 10 \frac{ \mbox{MeV}}{\mbox{c}} = 5.6 \times 10^{-21} \frac{\mbox{kg} | + | <math>mv = P = 10 \frac{ \mbox{MeV}}{\mbox{c}} = 5.6 \times 10^{-21} \frac{\mbox{kg} \cdot \mbox{m} }{\mbox{s}} </math> |
Spent the remaining beam time doing radiation footprint measurements. | Spent the remaining beam time doing radiation footprint measurements. | ||
Revision as of 04:31, 29 July 2010
Design
New deisign: We changed to use just one magnet.
File:Emittance Test Optim File.txt
HRRL had steer magnets on itself. We don't need external steer magnets. But Dr. Chouffani said that we might need them after quads, if the quads are not on axis. He will think about it.
Beam Line design on 27th, Jul. 2010:
Optim File on 27th, Jul. 2010:
File:Emittance Test Optim File 27th Jul 2010.txt
Faraday Cup
Old Beam Line
Beam Line Parts
Constructed Beam Line for Emittance Test
Vacuum pressure on the beam line is less than torr (on 2010-July-7th).
Leveling Survey
Downstream of the beam up by 2.6 mm.
How to do Leveling Survey and Alignment with Theodolite on e- Beam Line
A. Leveling Beam Pipe
1. Put the theodolite as high as the center of the beam line at upstream. Turn theodolite up and down. If the up angle is equal to down angle from the center of the pipe, theodolite is exactly as high as beam pipe. If not, adjust theodolite, until up and down angles are equal.
2. Once first step finished, then rotate theodolite horizontally to down stream. Turn it up and down, if up and down angles are not equal, adjust the stand till they are equal.
B. How to Make Sure the Quad is Perpendicular to the Beam Line
If the distances between quads and end of cavity at any given points are equal, then quad and end of cavity are parallel. Pipe is perpendicular to the end of the cavity, thus, magnet would also be perpendicular to the pipe.
I will find at lest three random points quads and three corresponding points at the end of the cavity, make sure they are equal, then I can say, magnet is perpendicular to the beam line.
I am planning to stick a metal ruler two, so two faces are parallel.
C. Centering the Quad Magnet with Theodolite
Vertical Centering
1. Finish the step 1 in A.
2. Then turn up the theodolite from the upper edge of the pipe to the magnet hole, call this angle upper angle. Do the same at lower part, call it lower angle. If the this two angles are not equal adjust the stand till they are equal.
Horizantal Centering
We know the diameter of the pipe . So, we can calculate from the pipe to the edge of the quad as:
We need to make sure this distance is same when measure it horizontally, so that our quad is centered on the pipe. I am going to use a ruler to ...(thinking)
July 2010 Run
- Initial Accelerator Settings
E = 10 MeV Control Voltage= 4.09 V
Pulse Width <= 50 ns
Average Beam Current = least amount needed to light up YaG crystal, start at 1 mA and Rep rate of 100 Hz.
At the same time we want to do radiation test on HRRL. This is for predicting the radiation after shifting cavity to new position. Radiation test run plan is at: [1]
7/26/10
Alignment check
1.) Survey the Quad to be sure it is centered on the beam pipe
2.) survey the flag to determine if target is centered on the beam pipe
Transmission tuning
1.) Using the quads and accelerator coils, focus the beam on the YaG crystal to as fine a spot as possible. Monitor the FC during the focusing.
changed control Voltage from
Control Voltage= 4.9 V E = 16 MeV
to
4.09 V E = 10 MeV
Tune the 4 accelerator coils for max transmission.
We want to maximize the current reach the Farady Cup. This can be determined by the ratio on Channels of FC and Gun Current.
Gun current is the current on the pick up coil, which is input current for cavity. Current on Farady cup is the current reach the end of the beam line (FC is at the end of the beam line). We want to maximize the the ratio of Farady cup current to Gun current (FCC/GC), so there are more electrons will make it to the target. Thus, we enlarge our positron yield.
Basic principle: Fix three coils, change one till it maximized.
| Coil 1 upstream left/right (mA) | Coil 2 upstream UP/down (mA) | Coil 3 downstream up/down | Coil 4 downstream left right | Scope Picture | Gun Current | FC current | Transmission Gun / FC |
| 10 |  |
15 +/- 0.65 nV s | -5.41.8 nV s | 36 12 % |
The HRRL went down after 2 hours of operation.
7/27/10
No HRRL beam time today. Chad tested the Thermatron module and believes it is not the problem. Chad will continue debugging tomorrow.
Filament
convert files to pnm.
pnm: portable network map
JPG format:
BMP format:
Wiki won't allow me to upload with bmp extension. So, I used png extension to upload. After download files, you will find they are still with bmp extension.
Tiff
7/28/10
Maximize Transmission
Maximized setup according to the accelerator operator.
Beam Energy: 16 MeV
Rep Rate: 95 Hz
Pulse Width: 100 ns
| Coil 1 upstream left/right (A) | Coil 2 upstream UP/down (A) | Coil 3 downstream up/down (A) | Coil 4 downstream left right (A) | Scope Picture | Gun Current | FC current | Ratio | Spot Size | |
| 0.1 | 0.5 | 3.1 | 0.7 | 100px |  |
Reversed the polarities on coil # 3 and coil # 4. Rep rate: 3Hz
| Coil 1 upstream left/right (A) | Coil 2 upstream UP/down (A) | Coil 3 downstream up/down (A) | Coil 4 downstream left right (A) | Scope Picture | Gun Current | FC current | Ratio | Spot Size | |
| 1.2 | 1.2 | 0.0 | 3 | 100px |  |
It appears the the image from electrons hitting the YaG crystal is offset (to the right) compare to the image from the filament which appears near the center of the cross hairs.
Electron beam deflection du to eartch B-field.
Is the earths Magnetic field causing the electrons to move this far beam right?
= 0.00005 Tesla (kg/C/s) = 0.5 Gauss
E_{electron} = 10 MeV = Pc \Rightarrow P = 10 MeV/c
Estimation using Classical Lorentz Force (forget about angle of B and V)
assuming v and B are orthogonal then we get the cyclotron radius
Spent the remaining beam time doing radiation footprint measurements.
7/29/10
repeat Quad scan
Change the linac coils to determine a setting which delivers the maximum current to the FC and has a reasonable spot size on the YaG viewer.
| Coil 1 upstream left/right (mA) | Coil 2 upstream UP/down (mA) | Coil 3 downstream up/down | Coil 4 downstream left right | Scope Picture | Gun Current | FC current | Ratio |
| 10 | 100px |
| Coil 1 upstream left/right (mA) | Coil 2 upstream UP/down (mA) | Coil 3 downstream up/down | Coil 4 downstream left right | Scope Picture | Gun Current | FC current | Ratio |
| 100px |
| Coil 1 upstream left/right (mA) | Coil 2 upstream UP/down (mA) | Coil 3 downstream up/down | Coil 4 downstream left right | Scope Picture | Gun Current | FC current | Ratio |
| 100px |
| Coil 1 upstream left/right (mA) | Coil 2 upstream UP/down (mA) | Coil 3 downstream up/down | Coil 4 downstream left right | Scope Picture | Gun Current | FC current | Ratio |
| 100px |
a.) Does a small beam spot size on the crystal give maximum FC signal?
b.) Is there a point where the spot size changes and you can't resolve a change in the FC output?
c.) Remove the YaG target and determine if above observations are unchanged.
2.) After tuning the beam to deliver the Maximum beam current to the FC, measure the FC and green pickup coil output as a function of current by integrating the pulse with an oscilloscope.
| FC output | Green Pickup Coil output |
| (mA) | (mA) |
| 10 | |
| 20 | |
| 30 | |
| 40 | |
| 50 | |
| 60 | |
| 70 |
a.) does the FC output change with rep rate? It should not but maybe there is loss at high rates?
Quad scan
First attempt to measure the spot size change as a function of Quad current
| Quad Current | Beam Spot RMS (0 degrees= Left/right) | Beam Spot RMS (90 degrees= Up/Down) |
| (Amps) | (mm) | (mm) |
Shall we do both polarities?
Imaging
Background subtraction
The filament produces at least a 2 mm diameter spot on the YaG crystal. Beam dominates the image.
7/30/10
Open day to finish leftover tasks
Consider emittance measurements at different energies.
Imaging scratch area
After image manipulation in GIMP to remove spot from filament. Obtained reasonable projections for horizontal and vertical beam sizes. The quad was off, low rep rate to avoid saturation, 10MeV. This was the spot for the initial setup on Wednesday.
Go back Positrons