PITZ layout

1
PITZ layout
EMSY layout
Emittance measurement principle
EMSY consists of two orthogonal actuators
perpendicular to the beam axis which are holding
the components which are inserted in the beam
line. Stepper motors are provided to move
separately each one of the four axes which give
the precise spatial positioning and orientation
of the components. EMSY was designed and
manufactured jointly of Sofia Institute for
Nuclear Research and Nuclear Energy and DESY
Zeuthen in the period 2000-2001.
The principle of slit based emittance measurement
is to cut emittance dominated beamlets from a
space charge dominated beam. The spatial spread
of the beamlets at distance L downstream
corresponds to the local spread of velocities of
the electrons in the beamlet which is expression
of the local divergence of the beam. The
normalized emittance is calculated using the
following formulas
General requirements
Beam used as input

• The beamlets produced by the slit mask must be
  emittance and not space charge dominated.
• The contribution of the initial beamlet size to
  the one measured at the observational screen must
  be as small as possible.
• The distance between the slit mask and the
  screen must be big enough to resolve small beam
  divergence.
• The mask thickness must be enough to scatter the
  residual electrons from the beam in order to
  produce an uniform background for the beamlets
  measurements and still it must provide sufficient
  acceptance angle.
• The precision of the slit motion is determined
  by the minimum rms size of the beam and the
  maximum number of transverse phase space samples
  needed to be taken. In our case minimum rms size
  is estimated to be 200 mm. The precision in
  positioning needed is better than 10 mm.
• The optical resolution of the TV system must be
  sufficient to resolve beamlet size down to 40 mm.

Optimization of the system
Beam dynamics considerations Resolution of the
system
GEANT4 model
The performance of the system is determined by
the expected beam dynamics, and the interaction
between the beam and the systems components.
Here the resolution of the system at 30 MeV is
shown (left up and down) as well as the results
from GEANT4 simulations representing the
interaction between the beam and the slit mask
and the beam and the YAG screen.
The model consists of two tungsten plates which
form the slit mask, steel pipe and 10 mm YAG
layer.
Here Cs counts signal Cn counts noise As
area of the signal An area of the noise
On the plot above is shown the maximum slit
opening as a function of the beam size at 30 MeV,
the emittance is fixed at 1 p.mm.mrad
here cb relative beam size grow at the
screen sb0 RMS size of the slit
The expected signal to noise ratio is shown on
the plot above. On the left hand side is shown
the energy deposition in the tungsten piece.
here L drift distance s0 RMS size of the
beam