HRRL OTR Test Feb 16th 2011

Objectives

1.) Check alignment of the OTR target and beam line with the linac's central axis. If it is misaligned we will work on an alignment plan to be executed after the Wednesday beam test.

2.) Take OTR images, check image focus and light output.

3.) Determine which quad to use for emittance measurements. Establish a quad current scan range.

Steps

Practise Turning HRRL On

Make document of the whole process, write a Standard Operation Process (SOP).

Turn RF off, Try to see Image with filament on

If we can see filament spot on the OTR target, try to focus our image system.

Turn RF On

Turn RF on look at the images, take pictures of the image upload them to the wiki.

Experiment

First Fusing

Image on OTR target

Lights	RF	image
on	off
on (different contrast)	off
off	off
on	on (27 Hz)

RF:25-205, Peak Current50mA, Pulse Width_200ns (fwhm)

RF:25, Peak Current60mA, Pulse Width_200ns (fwhm)

RF:50

Light is on

Second Fusing

Focused With Lenses,140 mA 58Hz 100ns

Determine the smallest energy, beam current, pulse width, and rep rate for a visible image.

Visible Image for Lowest Parameters

Second Focus

Following images are taken under conditions that: 100 ns FWHM pulse width, 25 Hz Repetition Rate:

Beam off

 20 mA peak current image is the lowest noticeable under 100 ns FWHM pulse width, 25 Hz repetition rate.

20 mA Peak Current

30 mA Peak Current

50 mA Peak Current

60 mA Peak Current

70 mA Peak Current

80 mA Peak Current

90 mA Peak Current

100 mA Peak Current

110 mA Peak Current

120 mA Peak Current

140 mA Peak Current

Estimation of Single Bunch Charge

S-band linac has RF frequency of 2856 MHz. The period then is:

[math]\displaystyle{ T_{RF}=\frac{1}{f_{RF}}=\frac{1}{2856MHz}=350~ps }[/math]

Pulse width of the RF macro-pulse : [math]\displaystyle{ \Delta t }[/math].

Number of bunches within a pulse: [math]\displaystyle{ N }[/math]

[math]\displaystyle{ N \times T_{RF} = \Delta t }[/math]

[math]\displaystyle{ N=\frac{\Delta t}{T_{RF}} }[/math]

Peak current of the pulse: [math]\displaystyle{ I_{peak} }[/math]

Total Charge in a macro pulse: [math]\displaystyle{ Q_t=I_{peak} \times \Delta t }[/math]

Charge in a single bunch: [math]\displaystyle{ Q_{s} = \frac{Q_t}{N} }[/math]

[math]\displaystyle{ Q_{s} = \frac{ I_{peak} \times \Delta t }{ \frac{\Delta t}{T_{RF}} } }[/math]

[math]\displaystyle{ Q_{s} = { I_{peak} \times }T_{RF} }[/math]

[math]\displaystyle{ Q_{s} = { I_{peak} \times }350~ps }[/math]

I_{peak} (mA)	Q_{s} (pC)
10 mA	3.5
20 mA	7
30 mA	10.5
40 mA	14
50 mA	17.5
60 mA	21
70 mA	24.5
80 mA	28
90 mA	31.5
100 mA	35
110 mA	38.5
120 mA	42
130 mA	45.5
140 mA	49

Average current

Area under the curve: A = 315.6 nsV.

Macro pulse [math]\displaystyle{ \Delta t }[/math] = 200 ns.

Average Voltage: [math]\displaystyle{ V_{ave} = A / \Delta t }[/math] = 315.6 nsV / 200 ns.

Scope impedance: R = 50 [math]\displaystyle{ \Omega }[/math]

Average Current: [math]\displaystyle{ I_{ave} = V_{ave}/R = \frac{315.6 nsV } {200 \times 50~\Omega ns} = 31.56~mA }[/math].

[math]\displaystyle{ Q_{s} = { I_{ave} \times }T_{RF} }[/math]

[math]\displaystyle{ Q_{s} = { I_{ave} \times }350~ps }[/math]

[math]\displaystyle{ Q_{s} = { 31.56~mA \times }350~ps = 11.046~pC }[/math]

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