Download + ultra ii

A CONCEPT FOR CHERENKOV TELESCOPES FOR ULTRA-II
Florian Goebel, Anton Kabelschacht, Eckart Lorenz
SUMMARY PHYSICS GOALS AND PROSPECTS
Study of the spectra of galactic point sources as well as extended galactic sources up to around 100 TeV•
Details of spectral cut-off parameters of these sources

Spectral shapes of low redshift AGNs with high sensitivity

All-sky monitoring with high sensitivity, alerts for the low threshold array and quick switchover to dedicated

sources in case of flaring sources
Study of diffuse gamma-radiation from the galactic plane

Study of possible isotropic gamma-emission from Topological Defects
Study of the chemical composition between 1012-1015 
Search for fine structures in the general CR spectrum
Long-term studies of some flaring sources
Possibly a search for quark-gluon plasma (needs theoretic input)
Extension of GLAST studies
No studies of GRBs 
May be: use of the array as an air fluorescent detector in the 1016-1018 eV range. Needs some bright ideas 
for the trigger, attractive for small groups
Coincidence studies with large VHE neutrino detectors for some dedicated source candidates. 
Crazy idea : study of high atmosphere small discharges (Elfs etc) see EUSO proposal. 
Search of extraterrestrial intelligence by using the array as an all-sky monitor for optical signals 
(proposal of ManeL Martinez)
BASIC DESIGN CONSIDERATIONS
IT IS IMPOSSIBLE TO BUILD AN OPTIMAL DETECTOR THAT SPANS 4 ORDERS OF •
MAGNITUDE IN ENERGY DUE TO THE STEEP POWER LAW OF FLUXES
ONE NEEDS TWO DETECTOR CONFIGURATIONS FOR THE CTA TO SPAN FROM•
≈ 10 GEV TO ≈ 100 TEV
LEA (≈ 10GEV - > 1 TEV) + ULTRA II < (1 TEV - >100 TEV)
ULTA II (ULTRA LARGE TELESCOPE ARRAY) 100 TELESCOPES SPREAD OVER 1-2 km2•
EACH TELESCOPE WITH ≈ 18 m2 MIRROR AREA•
SENSITIVITY ≈ 10 x HIGHER THAN PAST ARRAYS•
LOWER THRESHOLD LIMIT : ≈ 400 GEV IN ZENITH POSITION BUT HIGH g/h SEPARATION•
POWER AT ≈ 1 TEV
UPPER OPERATION LIMIT ≈ 200 TEV•
TELESCOPE CONFIGURATION: BLEND OF HEGRA TYPE CONSTRUCTION (LOWER PART)•
AND MAGIC CONSTRUCTION (UPPER PART)
SOME SPECIAL ISSUES
THE TECHNICAL CONSIDERATIONS ARE NOT VERY CHALLENGING COMPARED•
TO THE LEA PART
THE DOMINANT COST IS DRIVEN BY THE CAMERA -> USE OF CLASSICAL PMTS•
-> USE OF 25 mm HEMISPHERICAL PMTS (CONSERVATIVE, LOW RISK, PLENTY
OF EXPERIENCE, NO NEED TO MAXIMIZE QE, PANEQUE LACQUER OK,
PMTS MATURE, G-APDS STILL IN EARLY DEVELOPMENT PHASE)
INSTEAD OF INVESTING IN IMPROVING QE BY FANCY WORK- •
-> INCREASE MIRROR AREA-> 18m2 (> 2x HEGRA IACT AREA)
NEARLY ENTIRELY TO BE CONSTRUCTED BY INDUSTRY: •
ALL WORK CAPACITY NEEDED FOR HESS II, MAGIC II AND LEA
AIM FOR CONSTRUCTION TIME ≈ 4 YEARS•
INSTALL A TELESCOPE BY 4-5 PEOPLE IN < 1 WEEK•
SOME TECHNICAL ISSUES
FOUNDATION: a la HEGRA : SIMPLE CONCRETE BLOCK 3 x3x1 m3 + thin working platform•
UNDERCARRIAGE: LIKE FOR HEGRA CTS WITH CRANE BALL BARING•
PLUS ROTATING WORKING PLATFORM
UPPER STRUCTURE LIKE MAGIC SPACE FRAME- ALUMINIUM TUBES•
BUT ONLY 2 LAYER SPACE FRAME USING A TETRAEDER AS BASIC ELEMENT
DRIVE MOTORS: STEPPING MOTORS LIKE FOR HEGRA•
CAMERA SUPPORT MAST: GOTHIC ARC (PREFORMED I-BEAM) HOLD BY•
PRESTRESSED STEEL CABLES
MIRRORS: HEXAGONAL, MADE FROM HIGHGLY REFLECTIVE AL-ANOD PLATES•
SUPPORTED BY HEXCELL SANDWICH (a la CURRENT PADOVA CONSTRUCTION)
NO NEED FOR DIAMOND MACHINING
HIGH WEATHER RESISTANCE DUE TO MULTILAYER COATING
POORER FOCUSSING THAN IN MAGIC BUT OK BECAUSE OF 0.25° PIXELS
ALTERNATIVE MIRROR PRODUCTION : REPLICA METHOD - WUERZBURG•
ALTERNATIVE MIRROR PRODUCTION: THIN ALUMINIZED GLASS FOILS BACKED BY •
HEXCELL SANDWICH
NO ACTIVE MIRROR CONTROL BUT AUTOMATIC MIRROR ADJUSTMENT EVERY•
1-2 MONTH
SOME TECHNICAL ISSUES, II
CAMERA : 5° Ø, 0.25° PIXEL SIZE -> ALMOST MAGIC LAYOUT INNER SECTION•
FOR f = 7 m
-> COPY OF MAGIC I PRINTED CIRCUIT
PMTS 6 STAGE PMTS (GAIN≥ 105) + TRANSIMPEDANCE PREAMP•
BANDWITH CAN BE LOWER THAN FOR MAGIC PMTs
DYNAMIC RANGE OF PREAMP ≈ 500 SUFFICIENT
ET SAYS THAT PRICE FOR 33000 PMTS CAN BE € 100/PMT IF NO UV GLAS NEEDED•
ET CAN BUILD CAMERA PRINT CIRCUIT, TEST AND ASSEMBLE, HT + PREAMPS•
SHORT COAX CABLES (RG174) FROM CAMERA TO READOUT ELECTRONICS •
LOCATED IN SPACE FRAME
CAMERA WINDOW: UV TRANSMITTING PLEXIGLASS•
LIGHT CATCHERS a la MAGIC, LINED WITH POSSIBLY DIELECTRIC MIRROR FOIL•
HT: IN CAMERA, NEW COMPACT VERSION•
DIGITIZER: SWITCHED CAPACITOR ARRAY (DOMINO CHIP) ACTING BOTH AS •
DELAY AND F-ADC (500 MHZ, HIGHER FREQ. NOT NEEDED). MAIN PROBLEM
CURRENT READOUT MUCH TOO EXPENSIVE -> CUSTOM IC
TRIGGER: RATHER SIMPLE: 2 FOLD NEXT NEIGHBOR FOR EACH TELESCOPE•
+ 2 FOLD COINCIDENCES BETWEEN 1,2,… OF THE 6 NEXT NEIGHBOR TELESCOPES
WILL START READOUT OF DOMINO (TRIGGER RATE 25-40 hz)
OTHER PHYSICS (FLUORESCENCE DETECTORS MIGHT NEED MORE COMPLEX•
LOGIC)
USE OF DIGITAL SIGNALS VIA OPTICAL FIBERS WHENEVER POSSIBLE•
SUMMARY TELESCOPE PARAMETERS
mirror area: ≈ 18 m2
1.
Mirror layout: see Fig 1
2.
Focal distance 7 m (f/D ≈ 1.4)
3.
Number of mirror elements: 18
4.
Mirror profile: quasispherical, Davis-Cotton
5.
Operation range: Azimuth: 350°, Declination + 100°-> -75°
6.
Camera diameter ≈ 5 °
7.
Pixel size 0.25°
8.
Nr of pixels ≈ 330
9.
Photon sensors: PMTs, 1’’ Ø, hemispherical, 6 dynodes, max gain 105 10.
Max slewing speed: 60°/min (fast slewing not needed) 11.
Drive motors: stepping motors with planetary gears of small backlash 12.
Angular measurements: by 13 or 14 bits absolute shaft encoders read out by CAN bus
or equivalent bus
.13
Trigger: each telescope: two next neighbour pixels. Between telescopes: wide gate coincidence
14
triggering coinciding telescopes. Under normal conditions at least 2 telescopes should trigger in
coincidence. Alternatively, for all sky monitor observations, telescopes trigger autonomously.
For air fluorescence studies a special trigger is needed
Pulse digitizing: 1024 deep switched capacitor array running at 500 MHz, ≈ 10 bit dyn. range.
Location of readout electronics: in small containment mounted in mirror dish and single fiber
optical connection to central electronics counting house.
High reliable and self-protecting electronics for near-remote operation
17
Clock: central GPS controlled clock with fiber optics fan-out to each telescope. Relative clock
time precision ≈ 1 nsec.
19
15.
16
18
SUMMARY TELESCOPE PARAMETERS
COST ESTIMATE
Cost per telescope: Total cost < 200 k€
Concrete foundation ≈ 5 k€

Mechanical structure: 25 k€

Motors, encoders, power: 10 k€

Mirrors: 10-20 k€

Camera +DAQ: 110 k€

Auxiliary equipment: 35 k€

1.
TOTAL COST OF ULTRA II
25 M€ = 5M€ DEVELOPMENT COSTS+ 100 TELESCOPES
If you need finer pixels: either more money or fewer telescopes.
For 0.12°pixels: either 3x fewer telescopes or price 75 M€
A POSSIBLE DEVELOPMENT ROAD
A) MONTE CARLO STUDIES
CROSS CHECK CORRECTNES OF HADRONIC SHOWER PHYSICS
SIMULATION OF SENSITIVITY, TRIGGER PERFORMANCE
•
•
B)LIST OF TECHNICAL DEVELOPMENTS
HIGH PRIORITY DEVELOPMENTS
.1
PROTOTYPE MIRROR DEVELOPMENTS
•
SPECIAL ASIC FOR DOMINO READOUT
•
TWOFOLD NEXT NEIGHBOR COINCIDENCE LOGIC
•
LOW POWER DISCRIMINATOR ASIC WITH EASY EXTERNAL CONTROL OF THREHOLD
AND DELAY
MEDIUM PRIORITY
.2
LOW POWER HT UNITS FOR PMTS
•
MECHANICAL DESIGN OF TELESCOPE STRUCTURE
ACTIVE MIRROR ADJUSTMENT
•
LIGHT CATCHER WITH DIELECTRIC REFLECTOR FOIL
PARALLEL STUDIES
.3
HIGH RELIABILITY AND ROBUST OPERATION CONCEPT
REMOTE OPERATION CONCEPT
•
COST CUTTING STUDIES
•
QUICK INSTALLATION CONCEPT
•
•
•
•
•
Not useful, cutoff in UV
Multilayer Quartz-TiO2
Price of MIRO 4300
per panel of 1250x1250 mm, 0.5 mm
20 panels for developments. : 80 €/panel resp. mirror
2000 panels: 25 € /panel resp. mirror
Note: 300G is not weather resistant
Mirror work at Wuerzburg
POSSIBLE MIRROR LAYOUT
LAYOUT MIRRORS (BLUE) AND TOP LAYER OF SPACE FRAME (BLACK)
LOCATION OF ACTUATORS/FIX POINTS OF MIRROR PANELS
ACTUATORS
LAYOUT MIRROR AND TOP
LAYER SUPPORT FRAME
CAMERA SUPPORT MAST
MIRROR
108 cm
CAMERA SUPPORT MAST
540 cm
BASIC SPACE FRAME ELEMENT MAGIC
BASIC ELEMENT FOR ULTRA
CONSIDERABLY STIFFER
PART OF TRIGGER LOGIC
≥2 PIXELS FIRING
ACQUIRE
≥2 PIXELS FIRING
ACQUIRE
POSSIBLE MODES OF OPERATION
HIGHEST SENSITIVITY FOR SINGLE SOURCE SEARCH/STUDY:
COMBINE LEA+ULTRA II AND FOCUS ONTO ONE SOURCE
‘ALL SKY MONITORING’: POINT ALL TELESCOPES TO DIFFERENT POINTS ON SKY
COVER ≈ 0.5 STERAD BUT WITH LOW SENSITIVITY
CAN ALSO BE USED AS A FLY’S EYE TYPE DETECTOR
VARIANT: COMBINE 3(2) TELESCOPES FOR STEREO SUBCELLS AND POINT TO
DIFFERENT POINTS ON THE SKY
COVERS ≈ 0.15 STERAD, BUT WITH HIGHER SENSITIVITY (≈2-3)
SPLIT ARRAY INTO TWO(2,3..) PARTS AND USE ONE PART FOR HIGH SENSITIVE
SOURCE STUDIES WHILE USING OTHER (SMALLER) PART FOR LONG-TERM
MONITORING OF DEDICATED FLARING SOURCES (AGNS) FOR VARIOUS STUDIES
….MONITORING TOGETHER WITH LARGE NEUTRINO DETECTORS…
CONCLUSIONS
A 100 TELESCOPE ARRAY CAN BE BUILD WITHIN 4 YEARS
(ASSUMES LARGE INDUSTRIAL SERIES PRODUCTION)
MOST DEVELOPMENT CAPACITY NEEDED FOR LEA PART
A COST OF 25 M € IS NOT UNREALISTIC
THE BALANCE BETWEEN THE WISH FOR BETTER PERFORMANCE AND LIMITED
BUDGET WILL BE BETWEEN THE NR OF TELESCOPES AND CAMERA PERFORMANCE
RELATIVE CONSERVATIVE APPROACH POSSIBLE, NO CHALLENGING NEW
AND UNPROVEN COMPONENTS NEEDED
READOUT ELECTRONICS + TRIGGER VARIANTS MOST DEMANDING
MC SIMULATIONS NOT MADE
MC SIMULATIONS WILL MOST LIKELY GIVE GUIDANCE FOR SOME CRITICAL
PARAMETERS SUCH AS TELESCOPE SPACING, PIXEL SIZE AND CAMERA FOV