EBPM kw 29-30
achievements
Kirsten Hacker
Summary
• Trombone fiducialization and
characterization of hyteresis and backlash
• Accurate measurements of ACC1 energy
changes and gun/laser phase changes
with trombone feedback active
• Scan of coarse signal over larger range
Trombone Fiducialization
Trombone group delay is 7.62 cm in data sheet
-d
For any beam movement d,
The trombone moves 2d =>
d
Position = diff +trombone/2
Beam moves
Distance -d
d
d
VM moves
-2d
Trombone moves
7.62/2 = 3.82 cm
BUT, the data only makes sense
if you scale the trombone position
with something closer to 15 cm
because…
Trombone calibration is not constant
over full range
Bump comes from
reflection in pickup:
changes location
with beam position
1.6 mm/V
10.4 GHz downmixed signal
2
27 mm
V
1
0
28.5 mm
29 mm
-1
27 mm
-2
-50
-40
-30
-3
2
x 10
-20
-10
0
mm
1.3 GHz downmixed signal
10
EBPM position (um)
30
1.4mm/V
21
10.4 GHz mixed
V
20
10
-2
-40
-30
-20
-10
0
29.2
mm
mm
-2
0
Trombone
0.95 mm
1.35 mm
3 mm
3.42 mm
7.2 mm
5.79 mm
14.1 mm
11.52 mm
Here 10 cm trombone length scaling used between end switches
Scale according to signal wavelength NO
Scale according to slope YES => multiply poti by 1.14/2
-1
0
-1-50
VM change
1
2
3
4
28.920mm 30
10
5
6
potentiometer (um)
7
8
9
10
4
x 10
76 mm
Doesn’t actually move here!
Or here!
reality check
2000
1500
1000
EBPM and PM positions (um)
Nevertheless,
Measurement is reproducible
And accurate with
15 cm trombone scaling
500
0
-500
-1000
-1500
reality check
2000
-2000
1500
-2500
130.5
131
131.5
ACC1gradienttromboneonV Monday 2130.5131.90.1.txt
EBPM and PM positions (um)
1000
500
0
-500
Legend:
-1000
EBPM
-1500
-2000
-2500
130.5
PMT monitor
131
131.5
ACC1gradienttromboneonV Monday 2.1130.5131.90.1.txt
132
132
reality check
1000
1000
EBPM and PM positions (um)
1500
500
0
-500
-1000
-1500
130.8
500
0
-500
-1000
131
131.2
131.4
131.6
ACC1gradient130.9131.90.01.txt
131.8
BUT!
If *something* is jittering a lot,
The fine measurement of the monitor
cannot correctly
calibrate itself and the measurements
Are polluted by trombone hysteresis
And inaccurate calibrations
The situation can be improved
through averaging and reducing the
sensitivity of the trombone feedback
-1500
130.8
132
131
131.2
131.4
131.6
131.8
ACC1gradienttromboneoff130.9131.90.05.txt
132
reality check
2000
1500
EBPM and PM positions (um)
EBPM and PM positions (um)
reality check
1500
1000
500
0
-500
-1000
-1500
-2000
130.8 130.9
131 131.1 131.2 131.3 131.4 131.5 131.6 131.7 131.8
ACC1gradienttromboneoff130.9131.90.01.txt
reality check
2500
2000
EBPM arrival (fs)
1500
When the beam is jittering a lot,
it is better to use the coarse signal option1000
500
of the EBPM
0
-500
-1000
-1500
reality check
1500
-2000
-2500
130.8
EBPM and PM positions (um)
1000
131
500
0
-500
-1000
-1500
130.8
131
131.2
131.4
131.6
ACC1gradientcoarse130.9131.90.1.txt
131.8
132
131.2
131.4
131.6
ACC1gradientcoarse130.9131.90.1.txt
131.8
132
Typical parasitic measurements
PMT monitor
reality check
EBPM and PM positions (um)
1000
500
EBPM
0
-500
-1000
-1500
8
10
12
14
16
hours
18
20
22
-3
Correlation coefficients
PMT
VS
EBPM
1
0.63
0.40
PMT
0.63
1
0.37
VS
0.40
0.37
1
EBPM
PMT
VS
PMT
EBPM
3
VS
EBPM
1
0.938
0.886
PMT
0.938
1
0.885
VS
0.886
0.885
reality
check
reality check
x 10
4
% energy change
EBPM
5
2
1
0
1
-1
1200
EBPM
PMT
-2
20
1000
25
30
35
40
hours
45
50
55
60
800
position (um)
600
400
Drift over one setpoint
200
Trombone change at 46 hours
Wonderfully invisible
0
-200
-400
25
30
35
40
hours
45
50
55
Machinedrift22.txt