the whole OTR body, a modification of the target holder
that brings down the intersection between the optics line
and the target has been proposed. The mechanical layout
of the new holder is shown in Fig. 3. In this way the whole
body has to be lowered only by 1.52 mm instead of 7 mm
avoiding the wakefield effect. This new target holder will
be installed in June 2012.
allows one to reconstruct the complete transverse covari-
ance beam matrix, this also gives the values of the intrinsic
emittance [6].
Figure 5 shows a comparison between 2D and 4D al-
gorithms. If the incoming beam has no coupling the 2D
projected emittance will grow when one couples the beam
using a skew quadrupole. The calculated 4D intrinsic emit-
tance should remain constant. A scan of the QK1X skew
quadrupole intensity was performed in simulation. A test
of the 4D algorithm will be done in June 2012.
3-
30
25
A'20
Figure 3: New holder with a hole to introduce the target.
The metallic surface is lowered closer to the beam position.
EMITTANCE MEASUREMENT
The mOTR system is being used routinely for ATF2 tun-
ing activities. Its performance has been compared with that
of the WS. For example, Figure 4 shows a set of vertical
beam size measurements (by both mOTR and WS systems)
and the model (in solid line).
60
50
40
b 30
20
10
-mr
165 170 175
S [m]
Figure 4: OTR (OTR#X) and WS (M
parison. This set of measurements
run period of December 2011.
15
1 -0
-15 -10 -5 0 5 10 15
QK1X skew quadrupole intensity [A]
20
Figure 5: Simulation comparison between 2D and 4D emit-
tances when scanning QK1X skew quadrupole.
In order to have a real 4D emittance reconstruction more
research will be made on the algorithm and the OTR loca-
tions will be re-examined.
CROSS-PLANE COUPLING
CORRECTION
X r r In the diagnostic section of the EXT line, coupling cor-
0 0 0 rection after the DR is required to tune the beam in order
to reach the primary goal of ATF2. Two different algo-
rithms are proposed to correct the coupling. The so-called
scan method' consists of sequentially scanning each of the
single skew quadrupoles in order to find which intensity
minimises the measured vertical emittance. This method is
x >< x used routinely for beam tuning and works well. This is a
model-independent and robust algorithm.
180 185 190 Another proposed faster method is the so called 're-
sponse matrix method'. It builds the Jacobian matrix C
with elements Cz (a 1j/) which is the matrix of the
W#X) beam size com- linearly fitted coefficients between the intensity of the
was made in the ATF2 skew j and the coupling term measured at OTR i. Once C
has been built
The emittance has been measured using both 2D and 4D
emittance reconstruction algorithms. With the 2D method,
one is able to obtain the projected emittance. The 4D al-
gorithm recently implemented in the ATF2 control room
This methods were simulated and the result is shown in
Figure 6, where the angle in a profile monitor just after the
IP (MSPIP) is plotted against the angle at the entrance of
the EXT line.
-e- 4D
-- 2D
h E
I _-TT
