May 14th 2004 RD42 collaboration meeting 1

Results with a CVD diamond at Results with a CVD diamond at the K2K beam-linethe K2K beam-line

Jun Kubota(Kyoto Univ.)

RD42 collaboration meetingMay 14th 2004

ContentsContents1.Introduction1.Introduction2.Set up2.Set up3.Results3.Results4.Summary4.Summary

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Kyoto Univ.

J.Kubota, K.Nishikawa, T.Nakaya, M.Yokoyama

J.Kameda(now, ICRR)

KEK

TRIUMF

Toronto Univ.

Japan

Canada

P.Kitching, A.Konaka

J.F.Martin, W.Trischuk(RD42)

Member

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1.Introduction1.1 J-PARC neutrino oscillation experiment(T2K)

~1GeV beam

J-PARC50GeV PS

Super-K: 22.5 kt

Plan to start in 2009

Discovery of oscillationPrecision measurement of oscillation parameter

eμ νν

μμ νν

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In a long baseline neutrino oscillation experiment,it’s necessary to monitor the direction, the profile andthe intensity of the neutrino beam.

1.2 motivation

The neutrino beam can be monitored on spill-by-spill basison spill-by-spill basisby measuring the secondary muons coming from pion decay

A muon monitor is needed

(In K2K, silicon pad detectors and ion chamber are usedas muon monitors)

protonTarget

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1.2 motivation(cont.)

In T2K long baseline neutrino oscillation experiment,the muon beam intensity is expected to be 1000 times more than K2K

/yearμ/cm10 211 /yearμ/cm10 214In K2K, about In T2K, about

Radiation hardnessRadiation hardness for silicon detectorswill become a problem

Test whether a diamond detector is useful as a muon monitor- A diamond detector is installed to K2K muon monitor

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1.3 diamond detector

•Developed by RD42

•2 diamonds bought from Ohio State

Univ.-One packaged at Toronto, sent to KEK

-Second one still at Toronto

•Characteristic-Size 0.95cm 0.95cm

-Thickness 500

μm

Capacitance 9.1pF(as capacitor)

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2 Set up2.1 The position of the diamond detector

K2K neutrino beam line

200 m

silicon detectors ion chamber

3.5m

Beam dumpTarget

p

12GeVPS

K2K muon monitor

Muon intensity @ beam center ; ~Beam has 9 bunches for 1.1 , every 2.2sec

24μ/spill/cm10μsec

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2.1 The position of the diamond detector(cont.)

35cm

Beam center

diamond detectorsilicon detectorsion chamber

silicon detectors

We install the diamond detectoraround the beam center

The signal from the silicon detector is used as a referenceWe don’t know the absolute muon flux

Inside of K2K muon monitor

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HV supply

Diamond detector 9.1pF

capacitor 2200pF(to keep bias voltage)

about 20m

50 resistance

read out

w/o Amp

Time constant…about 0.46nsecOperate at the bias voltage of 650V

2.2 Circuit

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Beam spill has 9bunches for 1.1μsec

3mV

1.1micro-sec

2.3 Raw signal from the diamond detector

9 bunches are clearly observed, but,signal also has overshoot

overshoot

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3.Results

The relation of the collected charge v.s the electric fieldThe charge collection distancePhysical value defined by RD42

Measured item

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0.2

Electric field(V/ m)μ

1.0V/ mμ

1.0 1.2 1.40 0.4 0.6 0.8

0.02

0.05

0.070.06

0.04

0.01

0.03

0

3.1 The relation of the collected charge v.s the electric field

diam

ond/

sili

con

Above 1.0V/

almost flatμm

In RD42 measurement(NIM.A514(2003)79),reach plateau

1.0V/μ m

consistentconsistent

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Beam center

3.2 The charge collection distance

13.8pC(56.69ADC count)silicon detector160pC(656.1ADC count)average of two silicon detectors

measured ratio(diamond/silicon) 13.8pC/160pC… 8.6%

pedestal signal

@ m(650V)Measurement of the collected chargeMeasurement of the collected charge 1.3V/μ

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3.2 The charge collection distance(cont.)

Thickness of depletion layerAssumption… the collection efficiency;100%

The charge collection distance( )μm

The charge collection distance116.5 μm Possibly underestimate (>20%)

due to overshoot(shown by signal photograph)

measuredratio

μmsilicon

diamond

22000e/300

36e/2

22

2cm

cm(0.95)

300

μm μm

8.6%

Ratio(diamond/silicon)Ratio(diamond/silicon)Generated charge for a mip

Size

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SummaryWith a diamond detector, the signal of muon flux( ) was observed at K2K muon monitor

The relation of the collected charge v.s the electric fieldabove 1.0V/ , almost flatThe charge collection distance116.5 …possibly underestimate (>20%) due to overshoot (shown by signal photograph)-agree with the expectation(typical collection distance should be around 120 )

24μ/spill/cm10

μm

In T2K, we can conclude a diamond detector is usefula diamond detector is usefulas a muon monitoras a muon monitor

μm

μm

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Supplement

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Measured charge of the silicon detectorBeam center

169pC(693.2ADC count)

151pC(618.9ADC count)

160pC @diamond detector

Silicon detectorSize… 1cm ×2cmdepletion layer… 300micro-meter