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R. Battiston Consiglio di Sezione

Marzo 2008

Arrays of single photon tagging

telescopes for “non diffraction-

limited” optical application

ERC Senior grant call

R. Battiston

University and INFN Perugia


Marzo 2008


Marzo 2008

Since the time of Galileo, Cassini and

Tyco Brahe collecting and concentrating

light through mirrors and lenses mounted

on a telescope has been a most powerful

tools for the exploration of the universe,

amplifying weak signals from very distant

luminous objects.


Marzo 2008

Banda Ottica

EMISSONE TERMICA

~ 300 – 800 nm

T ~ 3000 - 10000 K


Marzo 2008

The sensitivity of these instruments is proportional tothe optical collecting area, that is to the square of thediameter of the primary optical element (D), often amirror.

Also the telescope resolving power and S/N ratios forpoint sources improve with the diameter of the optics,according to the formula sin = 1,22 l/D (Rayleighdiffraction limit), although for ground based telescopesthe blurring due to the atmosphere, which can bereduced with adaptive optics, is often the real limitingeffect for the resolving power.


Marzo 2008

Optical Collection

Refracting Telescopes• Lenses collect light

• BIG disadvantages

– Chromatic Aberrations (due to dispersion of glass)

– Lenses are HEAVY and supported only on periphery

• Limits the Lens Diameter

• Largest is 1 meter at Yerkes Observatory,

Wisconsin

http://astro.uchicago.edu/vtour/40inch/kyle3.jpg


Marzo 2008

Optical Collection Reflecting

Telescopes

• Mirrors collect light

• Chromatic Aberrations eliminated

• Fabrication techniques continue to improve

• Mirrors may be supported from behind

Mirrors may be made much larger than

refractive lenses


Marzo 2008

Optical Reflecting Telescopes

• Concave

parabolic primary

mirror to collect

light from source

– modern mirrors

for large

telescopes are

thin, lightweight &

deformable, to

optimize image

quality

3.5 meter

WIYN

telescope

mirror, Kitt

Peak, Arizona


Marzo 2008

Thin and Light (Weight) Mirrors

• Light weight Easier to point

– “light-duty” mechanical systems cheaper

• Thin Glass Less “Thermal Mass”

– Reaches Equilibrium (“cools down” to ambient

temperature) quicker


Marzo 2008

Hale 5 meter Telescope

Palomar Mountain, CA

http://www.astro.caltech.edu/observatories/palomar/overview.html

http://w

ww

.cm

og.o

rg/p

age.

cfm

?pag

e=374


Marzo 2008

LBT 2 x 8,5 meter mirrors


Marzo 2008

Large Optical TelescopesTelescopes with largest diameters

(in use or under construction:– 10-meter Keck (Mauna Kea, Hawaii)

– 8-meter Subaru (Mauna Kea)

– 8-meter Gemini (twin telescopes:

Mauna Kea & Cerro Pachon, Chile)

– 6.5-meter Mt. Hopkins (Arizona)

– 5-meter Mt. Palomar (California)

– 4-meter NOAO (Kitt Peak, AZ & Cerro

Tololo, Chile)

http://seds.lpl.arizona.edu/billa/bigeyes.html

Summit of Mauna Kea, with Maui in background

Keck

telescope

mirror

(note

person)


Marzo 2008

For these reasons (better sensitivity, resolving power and S/N) the frontier of

optical astronomy has alwas been focusing on the construction of very large

mirrors of optical quality; for example, the Extremely Large Telescope (ELT),

with a diameter of about 30 m, represents the most ambitious goal in this field for

the next decade (> 1 B project) .


Marzo 2008

• It is well known that the cost of the opticalelements increases with the size D,tipically like D2,5 to D2,7, posing severeconstraints on the feasibility of very largedishes or lenses. This proposal attempt tobreak this cost law by trying to replace onelarge optical units with several smallerunits, each equipped with electronicsdesigned such a way to be able toelectronically recombine and match (oreven improve) the performance of thesingle telescope, but at a significantlylower cost.


Marzo 2008

We start with non diffraction limited

optics: Cerenkov Telescopes A growing number of scientific applications are based on

the use of large “non diffraction-limited” optics, namely

optics where the ratio /D is much smaller than the

angular resolution required for the given application. An

important example of these applications are the ground

based Cerenkov Telescopes. The cost of these large,

powerful telescopes is rather high, approaching 10

M /unit and new plans of the international community

calls for the construction of arrays of these telescopes

(CTA), to enlarge by one order of magnitude both the

sensitivity and the energy reach of these instruments.

This new project will cost about 150 M of investment for

its construction.


Marzo 2008


Marzo 2008

A Fly’s Eye CTIdea: split CT optics into N smaller optics, each ofthem having

– The same F#

– The same # of pixel as the monolithic design

– An optimized optics (eg. Fresnel or Mirror or Lenses)


Marzo 2008


Marzo 2008

What is a SiPM ?

- Vbias

n pixels

One pixel

fired

Two pixels fired

Three pixels

fired

Current (a.u.)

Time (a.u.)

Al

ARC

-Vbias

Back contact

ppnn++

ppnn++

Rquenching

hh

p+ silicon wafer

Front contact

• matrix of n microcells in parallel

• each microcell: GM-APD + Rquenching

Main inventors: V. M. Golovin and A. Sadygov

Russian patents 1996-2002

Out

The advantage of the SiPM in comparison with GM-APD

ANALOG DEVICE – the output signal is the sum of the signals from all fired pixels

SiPM – photon detector candidate for many future applications

N. Dinu (Elba 2006)


Marzo 2008

INFN /PAT/ITC -irst MEMS project

• MEMS project devoted to the development

of detectors and MEMS (~6 M /three

years )

• Four pilot project

– SiPM for space and ground applications

– CMB detection arrays

– Cryogenic silicon

– 3D silicon


Marzo 2008

Wafer and SiPM design @ irst, ItalyMain blockWafer

SiPM geometric characteristics:

• area: 1 x 1 mm2

• number of micro-cells: 625

• micro-cell size: 40 x 40 μm2

SiPM

1 mm

1 m

m

N. Dinu (Elba 2006)


Marzo 2008S. Haino (INFN Perugia)


Marzo 2008

SiPM internal gain

Gain:• linear variable with Vbias

• in the range 5 x 105 ÷ 2 x 106

micro-cell capacitance• Cmicro-cell = 48 fF

-250x10-3

-200

-150

-100

-50

0

50

Vol

tage

(V

)

60x10-9

40200-20-40-60Time (s)

rise timerecovery time micro-cell recovery time

• = Rquenching · Cmicro-cell ~ 20 ns

Rise time• 1 ns (limited by the read-out

system)

0.0E+00

2.0E+05

4.0E+05

6.0E+05

8.0E+05

1.0E+06

1.2E+06

1.4E+06

1.6E+06

1.8E+06

2.0E+06

30 31 32 33 34 35 36

Bias Voltage (V)

Ga

in

N. Dinu (Elba 2006)


Marzo 2008

A look on photon detectors characteristics

10 ph.e 1 ph.e

No

sensitivity

No

sensitivity

100-

500V

< 100 V

200 105 - 106

few ns tens of ps

80 % 40%

60-70 % 50%

compact sensible,

bulky

1 ph.e 1 ph.e

Axial magneticfield 2 T

Axial

magneticfield 4 T

3 kV 20 kV

106 - 107 3 - 8x103

10 ps 100 ps

50 % 30%

APD GM-APD

60 %20 %20 %20 %BluePhoton

detection

efficiency 80-90 %40 %40 %40 %Green-

yellow

Red < 6 % < 6 %

MCP-PMT HPD

robust, compact, mechanically

rugged

sensible

bulky

Shape characteristics

100 ph.e1 ph.eThreshold sensitivity(S/N>>1)

No

sensitivity< 10-3 TOperation in the

magnetic field

10-100V1 kVOperation voltage

1106 -

107

Gain

tens ns 100 psTiming / 10 ph.e

90-100

%

< 6 %

PN, PINPMT

SOLID-STATE

TECHNOLOGY

VACUUM

TECHNOLOGY

N. Dinu (Elba 2006)


Marzo 2008

Single photon counting capability

0

1 p.e.

2 p.e.

3 p.e.

4 p.e.5 p.e.

6 p.e.

7 p.e.

LED at low-light-level to record the single photoelectron spectrum

Excellent single

photoelectron resolution

N. Dinu (Elba 2006)


Marzo 2008


Marzo 2008

Sparsification and Time Stamping

• Time stamping not needed, driven by the

readout clock

• Sparsification is highly desirable to reduce

the volume of data trasmitted off any chip

and to reduce the digital power dissipated

in the chip


Marzo 2008


Marzo 2008

Sparse readout

• Use token passing scheme (BTEV pixel readout) to sparsify theoutput

• Minimize the number of transistor/pixel as much as possible– During the acquisition a hit set a latch

– While reading out the first address a token scan ahead looking for thenext pixel to readout

– Time to scan 1 row = .125 ns x 450 = 56 ns

– Time to readout cell = 2 bit x 20 ns /bit = 40 ns

– TIme to readout 1 row = 20 x 40 ns =800 ns

Within one 0,8 μs slices the 200.000 SiPM array can be fullyreadout and put in a set of memories (a total of 10000 x 2 bits +addresses )

The content of the 100 array should be used to fill a computermemory with all the data, in order to implement the trigger logic.


Marzo 2008

R. Yarema


Marzo 2008

Critical analysis of the CT concept

•HV

•Dead space

•Hard to modify

geometry

•Expensive

•Available on the

market

•Long experience

•Radiation resistant

•Low noise

Pixellated

photomultipliers

•Very large mechanics

•Extends on all 3

dimensions

•Only one

measurement / FP

pixel

•Large mirror, free

standing, movable

•All the photons are

summed coherently

on the Focal Plane

•The trigger

electronics can be

embedded in to the

focal plane

interconnections

Monolitic optics

ConsProItem


Marzo 2008

Critical analysis of the CT concept

•New technology•Compact, robust

•Higher QE

•Smaller dead space

•Low Voltage

•Custom geometry

•Inexpensive

SiPM

•The trigger can only

be defined by

summing up the signal

from all the different

subdetectors

•Flat, compact

mechanics

•Measurement can be

splitted for

redundancy

•Suitable for stereo

view (with more than

one satellite)

•Higher quality optics

could be used

Multiple optics

ConsProItem


Marzo 2008

The EUSO detector concept

(from EUSO proposal)

Optics Light weight fresnel lenses

2m

Photo-détectors 200 000 pixels

Mechanics

Electronics :Analog - Digital

S.A. (LIDAR)


Marzo 2008

EUSO Optics

• 2 meter pupil 3.14 m2

• Double Fresnel lens

• ±30° FoV

• 6 arcmin (0,1°) resolution

• 330-400 nm sensitivity

• F1.0 - 1.25

• Diffraction limit 0.001 ( /D) arcmin

• (2 10-4 time the angular resolution)

• Pixel 4x4 mm2 , pitch 4,5 mm


Marzo 2008

Conclusions

• A novel approach is proposed to replace large mirrors with a

sum of coherently operating smaller units

• The availability of fast, inexpensive, single photon sensitive

solid state devices (SiPM) opens the window for this kind of

application

• INFN has the competence (SiPM with IRST, fast electronics,

digital processing with LHC….) to host this developement

• If successfull for CT this approach can be considered in space

(Super EUSO) and for astronomical telescopes

• If approved, collaborators from Perugia will be wellcomed

Arrays of single photon tagging telescopes for “non ... › sez › direzione › agenda › web...

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