Primary Proton Beam Profile Monitors-Segmented Secondary Emission Monitor-Outline
Introduction
Beam test at KEK-PS Neutrino Beamline
Summary1

Introduction
Desired Performance of profile monitors
at the J-PARC Neutrino beamline
High intensity proton beam induces large radiation dose.
Low material, long lifetime, easy to be maintained(In case of SSEM, movable structure will be required.)Dynamic range : Applied to beam intensity in the beginningof experiment. (1012 〜1014 protons/pulse)
Profile measurement resolusion required about 1~2mm.

2Principle of SSEM
SEM (Secondary Emission Monitor)
wire/strip
anode cathode anode
SecondaryelectronBeam

e-Thin metal foils are inserted
across the beam.
If the beam acrosses the foils,secondary electrons are emitted
from cathode electrodes, and areabsorbed by anode electrodes.

e-HighvacuumsignalSegmentation of cathodeelectrodes with wire/strips,enables to measure thebeam profile.

3

SSEM - Beam test : Purpose Requirement for SEM cathode materials
High efficiency of the secondary electron emission
Low amount of materials interrupting the beam
Resistant to heat and sputtering
Etc…
To Check the basic performance of SSEM
and to compare the cathode materials, wecarried out the beam test at the K2K
neutrino beamline.

Materials of cathode

Check the basic response of SSEM with
K2K proton beam (~6x1012 protons/pulse)
Compare the difference of signal
intensity among 5 cathode materials.

W Cu-Be TiCuAl4

SSEM - Beam test : Setup 10X10cm
1.5cm

Placed alternatively
at intervals of 7mm.
AlCathodeAnode

Beam size : vertical size ~4cm
: horizontal size ~2cm
Width of strip = 1.5cm. Æ require several nC/channel.

5SSEM - Beam test : Setup To Arc

To 1st dump
K2K-PS 12GeV
proton beam

Vacuum Chamber〜1e-06 Torr〜150m、Twisted pair cable

Oscilloscope

6

SSEM - Beam test : Basic responses signal pulse height [mV]

anode voltage dependence of the signal height
800
600
400

Beam Intensity : 〜4.3e+12 ppp

200
0100

200
anode voltage [V]300

Fig : Cu : ch2(center) pulse height
Hereafter, we set theConfirm one basic response :anode voltage to beSignal height was saturated around 100V.
200V.
7SSEM - Beam test : Basic responses Measured signal wave form (oscilloscope)
1 scale1.0V

Reference, Trigger
SEM used in K2K (Al:7µm , 5 foils)
Al:ch1

1 scale50mV

Al:ch2Vacuum:〜1e-06 Torr

Al:ch3-10

12Anode voltage 200V
34[µsec]

9 peak structure can be seen. （K2K beam: 9bunch/1pulse)

8

SSEM Beam test : Basic responses Beam position
centerAlCu
Ti
Cu-Be
W

relative Intensity

10

Beam position
upperFigure shows the relative
intensity to the highest
channel in each material.

10Beam position
lower

10

Change the beam positionfrom lower to upper.

ch3 ch2 ch1Ythethelowerch.

upperch.

In the measured profiles, there areclear response to the beam positions.
Beam profile does not depend on thecathode materials.

9SSEM - difference in cathode materials relative (Cu=1)
Secondary Emission Efficiency

Secondary emission efficiencies for the different cathode materials.
2

All measured secondaryemission efficiencies
are in the same order.

Cu-BeW

Ti
1Cu■：result of the 70MeV electron
beam experiment at SLAC.

AlNIM 39 (1966)p.303
00204060
atomic number80100ZTungsten is 4 times larger thanaluminum in interaction length.

Light materials, like
Al ,Ti, are preferable.

10SummaryIn this beam test at the K2K Neutrino Beamline
We confirmed the basic responses of SSEM.
Secondary emission efficiencies are in the same order in 5
cathode materials.
Æ In terms of interaction length, Al or Ti is preferable.

Preparation for the next beam
test at the K2K neutrino
beamline.
Ti strip(2mm)11