Study of MgB2 Thin Films on Nb by Pulse Laser Deposition

S.Mitsunobu, S.Inagaki, H.Nakanishi, M.Wake and M.Fukutomi*

KEK,NIMR*

Scope of talkScope of talk

IntroductionIntroduction

Forming method Mgb2 thin filmForming method Mgb2 thin film PLD equipment PLD equipment Precursor annealing Precursor annealing

RF Measurement of the MgB2 thin film and NbRF Measurement of the MgB2 thin film and Nb

Measurement of photo electron from the MgB2 thin Measurement of photo electron from the MgB2 thin film and Nbfilm and Nb

SummarySummary

INTRODUCTION

The large efforts have been concentrated on Nb cavities for International Linear Collider (ILC). The maximum accelerating field gradient of Nb cavities is limited about 50 MV/m due to Hcsh. MgB2 have higher Tc than Nb and expected to have higher Hcsh. Thin films of MgB2 on Nb is useful to increase future ILC energy upgrading.

At KEK, the preliminary test of thin films on Nb by Pulse Laser Deposition(PLD) method have been started and initially the direct deposition

of MgB2 film on Nb was studied.

Conceptual Drawing of Pulse Laser Deposition

Laser system of PLD

Vacuum Chamber of PLD

MgB2 Target

Substrate

PLD Processing

Heating 620oC in 1atom Ar

MgB2 film directly formed on Nb of 2.5mm thick

Heating 620oC

Q measurement system

Cu Cold test cavity

Q measurement system

QLs of MgB2 film on Nb & Nb

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Temp ( K)

QL QL(MgB2-Nb)

QL(Nb)

QL for Nb & MgB2 film

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Temp ( K)

QL QL(MgB2-Nb)

QL(Nb)

Photo electron measurement by PLD system

Nb MgB2 film on Nb

Relative Intensity of Photo electron

by 284nm laser wave length

Summery

• MgB2 precursor films formed on Nb by PLD.• The precursor film annealed at 620oC. • Cold RF measurement have been done.• The film partially superconducting.• Preliminary, photo electrons were measured for

Nb and MgB2. Some damaging of MgB2 surface was induced by defocused laser beam.

• More study will be continued.