1 km1 km22 array array version:version:

HHigh igh EEnergy nergy AAll ll SSky ky TTransient ransient RRadiation adiation OObservatorybservatory

HEHE--ASTROASTRO

By V. Vassiliev, S. Fegan

Ground based g-ray Astronomy: Towards the Future. October 20-22, 2005 UCLA

A E

$

Hardware implementationHardware implementation

ApproachApproach

TechnologiesTechnologies

Data Rates & Array TriggerData Rates & Array Trigger

Input parameters (from simulations)Input parameters (from simulations) To provide “fly’s eye” operation mode (+- 45 deg To provide “fly’s eye” operation mode (+- 45 deg

sky coverage) FoV >=15 deg is requiredsky coverage) FoV >=15 deg is required To sustain CR trigger rate at below 100kHz and To sustain CR trigger rate at below 100kHz and

operate in ~30-50 GeV domain FoV <25 deg operate in ~30-50 GeV domain FoV <25 deg must be usedmust be used

To trigger efficiently in this energy regime To trigger efficiently in this energy regime “effective” trigger pixel size must be in 0.1-0.2 “effective” trigger pixel size must be in 0.1-0.2 deg rangedeg range

To reconstruct events in “physics of the shower To reconstruct events in “physics of the shower limited regime” image pixel size must be in the limited regime” image pixel size must be in the range 0.01-0.02 deg.range 0.01-0.02 deg.

Optimal pixel size for triggering and imaging Optimal pixel size for triggering and imaging differ by a factor of ~10. (by 100 in units of differ by a factor of ~10. (by 100 in units of number of “effective” pixels in the camera).number of “effective” pixels in the camera).

Cost EmbarrassmentCost Embarrassment FoV =15 deg is ~180 degFoV =15 deg is ~180 deg22

This is equivalent to ~10This is equivalent to ~1044 “trigger pixels” or 10 “trigger pixels” or 1066 “image pixels” “image pixels”

To have IACT telescope for <=$1M and FP To have IACT telescope for <=$1M and FP instrument <= a few $100K the cost per trigger instrument <= a few $100K the cost per trigger pixel must be in the $10-100 range, and the cost pixel must be in the $10-100 range, and the cost per image pixel must be in $0.1-$1.0 rangeper image pixel must be in $0.1-$1.0 range

Current MAPMTs and MCP based MAPMTs are in Current MAPMTs and MCP based MAPMTs are in the range $40-$60 per channel. Current PMTs are the range $40-$60 per channel. Current PMTs are in the range above a few $100 depending on the in the range above a few $100 depending on the size and some other factors.size and some other factors.

Oups! To be suitable for imaging with required Oups! To be suitable for imaging with required resolution in 10 years from now the MAPMTs must resolution in 10 years from now the MAPMTs must drop in price by a factor of 10 each year. This can drop in price by a factor of 10 each year. This can only happen if market of these things will only happen if market of these things will increase so much that every family on the planet increase so much that every family on the planet will need one. This is not going to happen!will need one. This is not going to happen!

FP plate scale mismatchFP plate scale mismatch Something very inexpensive with very high level Something very inexpensive with very high level

of integration is required such as CCD or CMOS of integration is required such as CCD or CMOS image sensors, or perhaps arrays of SiPMs if they image sensors, or perhaps arrays of SiPMs if they are developed and made cheap.are developed and made cheap.

Oups! This devices are very small and to be used Oups! This devices are very small and to be used as FP instrumentation they would require as FP instrumentation they would require substantial optical processing of the image to substantial optical processing of the image to change plate scale without further image change plate scale without further image distortion. This results in prohibitive light loss in distortion. This results in prohibitive light loss in many optical elements and to compensate this many optical elements and to compensate this would require further increase of the telescope would require further increase of the telescope aperture thereby increasing plate scale mismatch aperture thereby increasing plate scale mismatch problem.problem.

Before optical image is conditioned to a small Before optical image is conditioned to a small CMOS or CCD plate scale it must be amplified!CMOS or CCD plate scale it must be amplified!

Fine image resolution utilizing CMOSand CCD technology

Fast Gated Image Intensifierto reduce NSB

Wide field of view optics; possibly of RC type

Moderatesize primary(3-7m)

Large aperture II (Electrostatic or MCP(?)) with extremely rapid image decay time

Array ofMAPMTs

1963 Japan: SugaItaly: ?Russia: ?

The Story of Ground Based The Story of Ground Based -ray Astronomy -ray Astronomy (by Jelley & Porter)(by Jelley & Porter)

All sky covered with 80 mega pixels in the CMOS sensor arraysOptimized Baker-Nunn optical system with three corrector normal lenses made of acrylic resin and 1 m spherical reflector (spot size less than 1 arcmin, 0.016o, for parallel light rays incident at angles less than 25o).Focal sphere image intensifier, FIIT, of ~60 cm aperture

Energy range> 1 TeVReadout Event Rate< 1kHz

Focal Plane InstrumentationFocal Plane Instrumentation

X-Y

Large ApertureImage Intensifier(Electrostatic or MCP)Photon detectionefficiency ~30-50% Fast decay scintillator output screen ~25 ns

Trigger Sensor~8200 pixelswith 0.146o

e.g. Array of rate compensatedDiscriminators

Star trackerVETO

Slow Control

X = ∑xi

Y = ∑yi

OR

Two-mirrormodified RC optical system

Primary 3-7mFov 15o

OpticalSplitter

Optical or II-based delay

Gate & Shutter

Gated Image Intensifier (MCP)(25-40 mm)Gate ~20nsRep. rate ~40kHzP-43/P-24 , ~2sec

Fast random access CMOS sensorImage pixel size – 0.0146o

Readout image – 128 x 128 pixelsReadout Image size – 1.875o x 1.875o

Readout rate 30-40 kHz

Amplified Image

CMOS Image SensorCMOS Image Sensor

Micron-MT9M4131.3-Megapixel CMOSActive Pixel DigitalImage Sensor

HE-ASTRO Image Sensor is not commercially available yet. However, industry is very close to meet specification. High-speedreadout is achieved with pipelineand parallel technologies.

Parallel processing macro-cell of32x32 pixels (1024) can be readout with > 500 kHz, and 128 x 128 pixelimage (16 macro-cells) with > 30 kHz

Image pixel size – 0.0146o

Readout image – 128 x 128 pixelsReadout Image size – 1.875o x 1.875o

NSB per pixel – 0.032 (20 nsec gate)ADC – 8 bit (S/N improved, 10– >8)Pixel dimension 12m x 12mSensor area – 12.3 mm x 12.3 mmShutter exposure – a few sec

Ashra CMOS image sensorAshra CMOS image sensor Ashra collaboration had Ashra collaboration had

worked with FillFactory to worked with FillFactory to develop Ashra Fine Sensor develop Ashra Fine Sensor (2048x2048 pixels, 2D control (2048x2048 pixels, 2D control of shutter/exposure and of shutter/exposure and readout).readout).

Prototyping from existing Prototyping from existing LUPA 4000MLUPA 4000M

Readout module is being Readout module is being developed by Toshibadeveloped by Toshiba

Ultimate goal 128x128 Ultimate goal 128x128 macrocells with 24x24 pixelsmacrocells with 24x24 pixels

Status … unknownStatus … unknown

IBIS4 1.3 Megapixel

Rolling Shutter Image Sensor(LUPA 4000M)

Read out rate is probably a factor of a few x 10 lower than required

Ultrafast ImagingUltrafast ImagingDRS technologies Inc.

Variety of Ultrafast Cameras for Military applications

CCD based500fps to 100,000,000fps e.g. 350 KHz at 250 x 250 Pixel exposures from 5 nseclimited number of frames

120mm tank gun projectile

airgun pellet impacting a matchstick

Photron CMOS based high speed camerasUltima APX-RS one of the fastest video cameras with 3,000 mega pixel frames per second (fps) or 250,000 fps at reduced resolution FASTCAM-X 1024 PCI is the first system to bring mega-pixel CMOS to your personal computer at usable speeds; capable of operating as fast as 1,000 fps at full 1,024 by 1,024 pixel resolution, or 109,500 fps through ‘windowing‘. Ultima APX-i2 uses a 25mm MCP Gen II image intensifier, directly bonded onto the APX's mega pixel sensor to provide unmatched image quality with 20ns gating.

Gated Image IntensifiersGated Image Intensifiers

Hamamatsu products

Type No. Effective Ares

Gate TIme &

RepetitionRate

Photocathode MCP Number

C9546-01 18 mm 3 ns, 30 kHz GaAsP 1

C9546-02 18 mm 3 ns, 30 kHz GaAsP 2

C9546-03 18 mm 3 ns, 30 kHz Multialkali 1

C9546-04 18 mm 3 ns, 30 kHz Multialkali 2

C9547-01 25 mm 5 ns, 30 kHz GaAsP 1

C9547-02 25 mm 5 ns, 30 kHz GaAsP 2

C9547-03 25 mm 10 ns, 30 kHz Multialkali 1

C9547-04 25 mm 10 ns, 30 kHz Multialkali 2

Available 25 mm 20 ns, 2 kHzGaAsP orMultialkali

1 or 2

Available 25 mm100 us, 100 Hz

GaAsP orMultialkali

1 or 2

Available 40 mm 20 ns, 2 kHz Multialkali 1 or 2

Available 40 mm100 us, 100 Hz

Multialkali 1 or 2

Left : C9016-2x Series & Controller Center : C9546 Series Right : C9547 Series

Commercial products which almost satisfy requirementsof resolution, repetition rate,and fast gating exist.

Trigger SensorTrigger Sensor

Hamamatsu H9500Flat Panel52mm squareBialkali Photocathode16 x 16 Multianode12 stage

FoV: 15o

Trigger pixel size: 0.146o

Number of MAPMTs: 32Effective Area Ratio : 89%Size: 312 mm

Trigger SensorTrigger Sensor

Hamamatsu H8500Flat Panel52mm squareBialkali Photocathode8 x 8 Multianode12 stage

FoV: 15o

Trigger pixel size: 0.205o

Number of MAPMTs: 69Effective Area Ratio : 89%Size: 468 mm

Trigger Sensor (alternatives)Trigger Sensor (alternatives)

Front illuminated SiPMs(Avalanche Geiger discharge) 3x3 mm2 square5625 pixels of 40µ x 40µ each

FoV: 15o

Trigger pixel size: 0.2o

Number of SiPMs: 1Effective Area Ratio : ~80%Size: 3 mm

BURLE 85011-501 PLANACON™ 71 mm square ( 51.2 mm active)Bialkali PhotocathodeMCP-PMT 8 x 8 pixelsNice single pe pulse

FoV: 15o

Trigger pixel size: >0.135o

Number of MCP-PMTs: 91Effective Area Ratio : ~52%Size: 710 mm

Courtesy ofR. Mirzoyan

Optical SystemOptical SystemRitchey-Chrétien configurationRitchey-Chrétien configuration

Field curvature coupled IIFor modified RC optical system the field curvature is convex toward the sky.

Primary 3-4 mFov 15o

To trigger

To single

camera

II

Increase of telescope aperture could be achieved by combining several midsize telescopes on the same mount and utilizing optical mixing (single camera) or digital mixing (multiple cameras – possibly more expensive). Various multiplexing options could be explored.

FP plate scale is matched with telescope aperture

Focal Plane Image IntensifierFocal Plane Image Intensifier

Photek manufactures a range of 18, 25, 40, 75 and 150 mm active diameter image intensifiers(too expensive and too small)

MCP Image IntensifiersElectrostatic Image Intensifiers

SIEMENS image intensifiers. Large aperture units (>40cm) are developedfor X-ray imaging.

Phosphor Scintillator P-47 - 80 ns <10%> decay timePhosphor Scintillator P-47 - 80 ns <10%> decay timeLanthanum Bromide Scintillator, LaBrLanthanum Bromide Scintillator, LaBr33 / LaCl3 - 25 ns <10%> decay time / LaCl3 - 25 ns <10%> decay time

High QE photocathode in 200-400 nm, >25%, continues to be an issue High QE photocathode in 200-400 nm, >25%, continues to be an issue

Telescope data pipelineTelescope data pipelineTrigger Sensor

TD &Veto Stars

GatedImage IntensifierP-43 ~2sec

TimingEvent

Identification

10 s Memory Ring

Buffer of Images

Indexed by local triggertimestamp

RetrieveImage to disk

II (int. ~20ns)delay

L1

ORL1i

L2TelescopeTrigger ~40 kHz

Gate 20 ns

Shatter 2sec

~1.0 Mpixel CMOSImage Sensor (1000-500 fps full frame)

1024x1024pixels

15o x 15o

Readout 128x128 Pixels1.9o x 1.9o

ADC 10 bits/pixel, 16384 pixels

Position encodingX = ∑xi, Y = ∑yi

Timing T

X,Y

Array trigger&

L2 Broadcast T

Zero suppression

~600 non-zero pixels (mostly NSB)

Bitmask 20 bitsADC 10 bits

~20kb per image

~2.3kbper image

Disk

~80Mb/s

Data rate = 80 Mb/s x 3600 s/h x 217 telescopes= ~62.5 Tb / array / hourSDSS 34 Mb/sLSST 10 Gb/s= 36 Tb/h

Array TriggerArray TriggerDistributed →Every node acts as its own array triggerDistributed →Every node acts as its own array trigger

Data rate to center node~24 Mbps @ 30 kHz

Telescope Trigger decision (~30 kHz)Telescope Trigger decision (~30 kHz) Local trigger → convert to GPS timestamp Local trigger → convert to GPS timestamp

(good to 100ns)(good to 100ns) Buffer timestamp locallyBuffer timestamp locally Broadcast “trigger packet” of timestamp and Broadcast “trigger packet” of timestamp and

node identifier (~5 bytes) to all nearest and node identifier (~5 bytes) to all nearest and next-nearest neighbors (max. 2Mbps outflow next-nearest neighbors (max. 2Mbps outflow rate)rate)

Local trigger together with any trigger of Local trigger together with any trigger of two telescopes from all neighbors and next two telescopes from all neighbors and next nearest-neighbors is recognized as array nearest-neighbors is recognized as array triggertrigger

Local processing at node Local processing at node • Receive trigger timestampsReceive trigger timestamps• Buffer trigger timestamps (10-20 μs) Buffer trigger timestamps (10-20 μs) • Search for a coincidence (compensate Search for a coincidence (compensate

for relative delays due to pointing)for relative delays due to pointing)• Coincidence → retrieve pixel data, Coincidence → retrieve pixel data,

write to disk (~80 Mb/s)write to disk (~80 Mb/s)

Array of 217 telescopesArray of 217 telescopes Elevation 3.5kmElevation 3.5km Telescopes’ coupling distance Telescopes’ coupling distance

80m80m Area ~1.0kmArea ~1.0km22 (~1.6km (~1.6km22)) Single Telescope Field of View Single Telescope Field of View

~15~15oo

FoV area ~177 degFoV area ~177 deg22

Reflector Diameter ~7mReflector Diameter ~7m Reflector Area ~40 mReflector Area ~40 m22

QE 50% (200-400 nm)QE 50% (200-400 nm) Trigger sensor pixel size 0.146Trigger sensor pixel size 0.146oo

Trigger Sensor Size ~31.2cmTrigger Sensor Size ~31.2cm NSB rate per Trigger pixel ~3.2 pe NSB rate per Trigger pixel ~3.2 pe

per 20 nsper 20 ns Single Telescope NSB Trigger Single Telescope NSB Trigger

Rate 1KHzRate 1KHz Energy Range 20–200 GeV Energy Range 20–200 GeV Differential Detection Rate Peak Differential Detection Rate Peak

~30 GeV ~30 GeV Single Telescope CR trigger rate Single Telescope CR trigger rate

~30 kHz~30 kHz

HE-ASTRO (specs)HE-ASTRO (specs) Image pixel size – 0.0146Image pixel size – 0.0146oo

Readout image – 128 x 128 pixelsReadout image – 128 x 128 pixels Readout Image size – Readout Image size –

1.8751.875oo x 1.875 x 1.875oo

NSB per pixel – 0.032 (20 nsec NSB per pixel – 0.032 (20 nsec gate)gate)

ADC – 8 bit (S/N improved, ADC – 8 bit (S/N improved, 10– >8)10– >8)

Pixel dimension 12mm x 12mmPixel dimension 12mm x 12mm Sensor area – 12.3 mm x 12.3 mmSensor area – 12.3 mm x 12.3 mm Shutter exposure – a few msecShutter exposure – a few msec Image integration time - 20 nsImage integration time - 20 ns Optical system TBDOptical system TBD Array trigger protocol TBDArray trigger protocol TBD Data Rates ~80 Mb/secper nodeData Rates ~80 Mb/secper node Online data processing TBDOnline data processing TBD

ConclusionsConclusions Large array of moderate size telescopes may provide a

viable cost effective solution to the problem of required large collecting area, large field of view, and low energy threshold at the same time, by combining new and reviving old ideas, e.g. using image intensifiers, but based on the contemporary technology.

Design of FP instrumentation requires innovative approach to resolution of a number of challenges. For example, cost vs # of pixels, large telescope aperture vs small imaging sensors (extremely light limited regime), large FoV vs high data rates.

Initial feasibility study of a possible implementation of FP instrument indicates that all critical to the project problems might be resolvable already in the next few years since the current state of technology is not too far from achieving required specifications.

Detailed feasibility study of proposed FP implementation concept as well as possible alternatives is required