Development of the Large Aperture EBCCD

○A. Suzuki, S. Aoki（Kobe Univ.）J. Haba（KEK)

M. Sakuda（Okayama Univ.）M. Suyama（Hamamatsu Photonics）

Contents

1. Motivation of development2. Specification of the EBCCD3. Basic performance

HV endurance & gainSpatial resolutionLinearity between input & outputCosmic ray detection

4. Summary

For example,the K2K SciFi detector[K2K Collab., A.Suzuki, et al., NIM A453(2000) 165-176]・ Many channel readout(11k fibers/IIT) ・1pe detection (high gain).

IIT

SciFi detector of K2K 24 IITs (φ10cm photocathode) and φ0.7mm fiber were used.

1. Motivation of developmentAs a same kind of photosensor as EBCCD, IIT has been used so far in particle physics experiments.

~

Electron multiplication is fluctuated at MCP and fluorescent plate.

Accelerated photoelectrons directly reach CCD and multiplied. → No fluctuation in

multiplication in principle

Good linearity between input and output is expected.

Photocathode

MCPFluorescent plate

CCD

EBCCD

IIT

high gain & large aperture EBCCD is desired!

If such one is used for readout of a scintillating fiber detector like the K2K SciFi detector,

・ good linearity in dE/dX measurement gives good PID.

・many channels can be read out at one time.

Therefore,

But EBCCD so far --- low gain & small aperture

2. Specification of the EBCCD

10cm

20cm

* Such a large aperture was realized by electron demagnificaton.

2. Specification of the EBCCDParameters Description / Value Unit

Spectral response 300 to 650 nmMaterial Bi-alkali --

Effective area

46×36 mm

Window material Fiber optic plate (FOP) --Magnification 1/5

Type FT-CCDEffectivearea 9.0 (H) × 6.7 (V) mm

# of pixels 640 (H) × 480 (V)Pixel size 14 × 14 μm

Target

Photo-cathode

3. Basic performance

HV endurance

Photocathode voltage (-kV)12

2400

Gai

n

1200

Good linearity !

Spatial resolution (1)Estimated from brightness distributions of ladder chart images

← Brightness distribution

X position [pixel]

Brig

htne

ss [a

rbitr

ary

unit]

Ladder chart image →

Brightness distributions0.25 lp/mm 0.5 lp/mm 0.625 lp/mm

1 lp/mm 1.67 lp/mm 2 lp/mm

We can see clear peaks and valleys up to 2 line pairs/mm (corresponds to 3.5 × CCD pixel size).

Spatial resolution (2)Estimated from an image of Cu foil pattern on a

fluorescent plate irradiated with X-rays (14 keV and 18 keV) and γ-ray (60 keV) form an Am source

２４１3cm

3mm50μm thick Cu foil pattern

Fluorescent plate(0.5mm thick)

Am

X-rayγ-ray

EBCCD

241

241

We could see gaps of ~0.25mm, corresponding to 2 lp/mm

Image of Cu foil pattern

Gaps between neighboring foils are ~0.25mm here

Linearity between output and input

• EBCCD output was measured as a function of input LED light.

• Input light intensity was monitored by PMT.• Same measurement was done for IIT to

compare.

Setup for the measurement

Blue LED(from the side of the fiber)

Scintillating fiber (φ0.7mm)

orIIT

EBCCDorIIT

Comparison of linearities

Light yield on PMT

EBC

CD

IIT

outp

ut (a

rb. U

nit)

EBCCD

IIT

Cosmic ray detectionby the scintillating fiber block

Cosmic ray

・Cross sectional view・φ0.7mm fiber

Effectivearea

46mm

36m

m

Cosmic ray track image

In spite of no gating, we can see a track!（1 frame image of several photoelectrons）

4. SummaryLarge aperture EBCCD was produced.

photocathode φ10cm. The 1st one with such a large aperture.

Some basic performances were measured.・HV endurance --- up to –12k

(Gain vs HV showed good linearity.)・spatial resolution --- better than 2 lp/mm ・good linearity between input and output

(better linearity than that of IIT) ・cosmic ray track detection --- OK!

• We are planning to develop an EBCCD with higher gain and gating function and use in particle physics experiment practically.

Image distortion

Image of 5mm spacing lattice Spacing on the CCD at various positions (unit in CCD pixel)

No significant position dependence of the spacingsSame result for 2mm spacing lattice→ Negligible distortion in the effective area (46mm(H)×36mm(V))

Brightness distributions for ladder charts(measured by IIT)

MTF vs spatial resolution

Spatial resolution [lp/mm]

MTF

EBCCD

IIT

MTF vs spatial resolution measured with Cu foil pattern

Development of the Large Aperture EBCCDContentsMotivation of development2. Specification of the EBCCD2. Specification of the EBCCD3. Basic performanceHV enduranceSpatial resolution (1)Brightness distributionsSpatial resolution (2)Linearity between output and inputComparison of linearitiesCosmic ray detection �by the scintillating fiber block Cosmic ray track image4. SummaryImage distortionBrightness distributions for ladder charts�(measured by IIT)MTF vs spatial resolution MTF vs spatial resolution measured with Cu foil pattern