TWO BEAMS (PERIOD 13) v. 01 (YMS)
1. Beam separation v buncher power (230kV) .
Bunch length from ASTRA sims . BC=-10/+40; 60pC.
two beam distance INJ-5 v Pb (SOL-02=2.80A) #2689 & #2885
20
14
deltaX(2.80A)
15
10
deltaX, mm
BUNCH LENGTH RMS, mm
deltaX(2.80A) #2885
1
2
3
12
8
10
6
4
5
2
0
0
0

5

10
15
20
SQRT(Pb)
25
30
35
40
0

Fig. 1.1
5
10
15
20
SQRT(Pb)
25
30
35
40

Fig. 1.2
Fig. 1.1.
RMS bunch length v SQRT(buncher power). ASTRA simulations. BC=10/+40; Q=60pC. Laser pulse = flat top, 28ps.
Curve 1 : entrance to the booster
Curve 2 : minimal bunch length in the beginning of the booster (~ 2-3 cells)
Curve 3 : exit from the booster
Fig. 1.2.
Distance between two beams on INJ-5 v buncher power. BC=-10/+40deg.
SOL-02 = 2.80A. Beam energy = 6.5MeV in #2885. Q=60pC (main part of the train)
The measurement (black curve) was made to repeat earlier one from Period 12 (red curve) .
Note in both cases - the effective bunch charge (first few bunches) is smaller than 60pC.
The two beams now are not that easy to single out (compared to Per 12). Overall trend is very
similar.
Different actual values could be due to the fact that #2689 (Per. 12), the accurate BC2 phase
was not measured and therefore could differ from +40deg.
Also, the effective bunch charge in first few bunches could be different now and then.
Fig.1.1 is to compare with Fig. 1.2. (and Fig. 4.4 in Per. 12 two beam report). The overall
behaviour of z (Pb) is not the exact replica of E(Pb) but has a good resemblance. Also –
the minima in both dependencies take place at ~ the same buncher power.
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2. Longitudinal separation between the beams (230kV).
Energy difference between beams was measured as a function of BC2 gradient while BC2
phase = +90deg. Data is in Fig. 2.1.
Two beams separation BC2=+90deg; #2885
Two beams separation BC2=+90deg; #2885
0.5
0.5
y = -0.52978 + 0.24633x R= 0.99692
y = -0.20363 + 0.089834x R= 0.99155
y = -0.69533 + 0.31108x R= 0.99879
y = -0.54843 + 0.25191x R= 0.99772
0.4
0.4
0.3
0.3
deltaE , MeV
deltaE , MeV
Pb = 1.0kW
0.2
0.2
Pb = 0.8kW
0.1
0.1
deltaE (1)
deltaE (2)
0
0
2
2.5
3
3.5
4
4.5
2
E2, MeV
2.5
3
3.5
4
4.5
E2, MeV
Fig. 2.1.
Fig.2.2
Fig. 2.1. Energy difference between the beams (INJ-5) v BC2 gradient (at zero-cross). Black
dots : data from single screen images with Dx=1.15m. Red dots – energy difference
calculated from the difference in DIP-01 currents. Beam energy was ~ 6.5MeV. BC2 voltage
is the “boonton” read back.
Pb=1.0kW
Fig. 2.2. The same data as in Fig. 2.1 with added data for Pb=0.8kW.
This experiment was just to replicate the one made in Per. 12. Solenoid settings (3.45 /
2.30A), Pb, and BC1 phase =-10deg were the same as in Per. 12.
NOTE: it was confirmed that the beam does not move or change shape on INJ-3 while
varying the BC2 in a full range.
For Pb=1.0kW:
Longitudinal distance between beams = 14.1o (=30ps; = 9.0mm).
The beams emerge from BC1 with energy difference of 530kV.
These numbers are close to those measured in Per. 12 (12.6o; 480kV)
Note : there is a small but clear difference in an angle of the straight line if only red dots or
only black dots used (above number are evaluated from “red” line).
2
Fig.2.3. Typical images at Pb=1.0kW: two beams on one screen (2.50MeV; left) and high
energy and low energy beams when they cannot be seen on one screen (3.26MeV).

For Pb=0.8kW (see Fig. 2.2) :
Longitudinal distance between beams = 5.2o (=11ps; = 3.3mm).
The beams emerge from BC1 with energy difference of 200kV
NOTE: the effective energy “chirp”, i.e. energy difference between the beams emerging from
BC1 divided by the longitudinal distance between them is identical for both 0.8 and 1.0kW
and equal to ~ 60kV/mm.
The two beam structure is much more accentuated at Pb=0.8kW compared to 1.0kW as can
be seen from Fig. 2.4.
Fig. 2.4. Two beams at Pb=0.8kW.
3
Two beams at 325kV
First attempts (#2869; #2883)
#2883. Study was hampered by phase instability hence actual phases are quite approximate.
Initial settings were either BC=-10/+20 or -15/+22. Pb=1.6kW.
It was possible to see two beams at some particular settings (see above). But variation of Pb
(both up and down) resulted in a loss of two beam structure.
Wide variation of BC1 phase (+10, -20) did not show structure.
Structure could be seen (but not reliably) at lower Q < 30pC.
As an example, three beams are clearly identified at Q ~ 20pC and BC2 = +90deg (#2869) :
#2869.
#2869. Some images of beam structure on INJ-5 from BC2 phase and GS scans (all at
Pb=1.6kW). Q=60pC.
BC=-15/+18deg
BC=-15/+90deg (BC2 = 0.84MV) 21:24
Beam structure can be seen but only at particular settings, i.e. not in a wider range of scanned
parameter.
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