Florian Goebel

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MAGIC - Camera and Readoutpresent future
Florian Goebel Max-Planck-Institut für
Physik(Werner-Heisenberg-Institut) München for
the MAGIC collaboration
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Key technological elements for MAGIC
Active mirror control (PSF 90 of light in
0.1o inner pixel)
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Light Sensors QE extended PMTs

• 6 stage PMTs (ET 9116A (1) , ET 9117A (1,5))
• characteristics
• - low gain gt operation under partial moon
• - rise time 0.6 nsec
• - FWHM 1.0- 1.2 nsec

stabilize HVPhK-D1gt stable Single PhE
response stabilize HVD5-D6 HVD6-A gt dynamic
range 5000
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Winston Cones

• avoid dead areas
• limit angular acceptance to light coming from
  reflector surface
• aluminized Mylar foil (92 reflectivity)

• increase double crossing probability gt
  increase effective QE

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Camera

• Matrix of 577 PMTs
• Field of View 3.5o

• Inner camera
• 397 pixels 0.1o
• Outer Camera
• 180 pixels 0.2o

optimized for sources in center of camera
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Camera Characteristics

• special features
• movable in z to adjust focal distance (1km - 8)
• Spectralon plate integrated in camera lids for
  focusing reflectivity measurements

• external HV power supply
• individual, remote adjustable HV regulators
• HV anode current monitoring (3 Hz)
• total power consumption 600 W ( 1 W /
  channel)
• water cooling
• gt temperature stabilization ? 3o
• total weight 600 kg

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Optical Transmission

• Analog signals transmitted over 162 m long
  optical fiber
• - noise immune
• - no signal dispersion
• - light weight

• Vertical Cavity Surface Emitting Laser (VCSEL)
• ? 850 nm
• multimode fiber
• E2000 connectors (eye safe, allows many
  connections)

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Signal Processing

• Split to high (10) low gain(dynamic range gt
  1000)

• Stretch pulse to 6 nsec

-gt FIFO
-gt single linux PC
-gt RAID system (100GB/night)
Ring Buffer
dead time lt 1 _at_ 300 Hz trigger rate
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Two Level Trigger
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Calibration System

• LED light pulses
• uniform illumination of camera
• 3 colors
• pulse shape like cosmics
• different intensitiesdynamic range 200
• Absolute calibration
• determine light intensity based on photon
  statistics (F-factor method)
• crosscheck with
• PIN diode
• blinded pixel (single PhE peak)

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Upgrades

• for MAGIC-II
• same concept (e.g. optical transmission)
• improvement for physics
• higher QE (PMTs, HPDs, SiPMs, see J. Ninkovic)
• faster sampling
• higher granularity (not for MAGIC-II)

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High resolution timing measurement

• Cherenkov pulses are 1-2 nsec wide
• Photosensors are fast enough
• gt digitize with ? 2 GSamples/s

• better background suppression
• reduce integration time 16 nsec gt 6 - 8
  nsec(MAGIC 0.1-0.2 pe/nsec)
• use time profile for muon rejection (under
  investigation)

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Multiplexing 2 Gsample/s FADC

• Idea use commercially available but expensive 2
  Gsample/s FADC to digitize several channels
• possible due to low duty cycle (trigger 1kHz,
  Signal 20 nsec)

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Optical Splitter Signal Multiplex circuit

• use optical fibers to delay signal
• low attenuation (3 dB/km)
• small dispersion

• Split optical signal into readout and trigger
  signal

• use 2 Gsample/s, 10 bit FADCs from Acqiris

• upgrade MAGIC I started
• currently running in test mode

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MAGIC-II Ring Sampler FADC

• freely propagating rotating sampling signal (? 2
  GHz)
• analog sampling in a series of 1024 capacitors
• slow (40 MHz) readout and external digitization

Design Stefan Ritt Paul Scherrer Institute
(Villigen,CH)

• Advantages
• low cost
• low power consumption
• very flexible

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MAGIC-II camera

• Cluster design
• 7 pixel cluster contains
• HV generator (DC-DC converter)
• slow control monitoring
• signal chain up to optical transmitter
• easier maintenance
• flexibility to exchange PMT with HPDs

FOV like MAGIC-I
but

• increase area with small pixels(add signal in
  outer pixels to save readout channels?)

• increase trigger area

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new in MAGIC-IILevel 3 (Two Telescope
coincidence)
Triggers (Level 2)
Programmable Delays
Delay Register
Coincidence Unit
L3 trigger
Trigger Flag
VME
L3 Pattern
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Conclusions

• MAGIC successfully employed several new
  technologies
• Upgrades MAGIC-III are under way
• Promising for future Cherenkov Telescopes