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EXPERIENCE WITH THE CONSTRUCTION AND OPERATION WITH THE MAGIC TELESCOPE E. Lorenz, MPI Munich WILL CONCENTRATE ON ISSUES RELEVANT FOR THE CONSTRUCTION OF POSSIBLE FUTURE LARGE IACTS A FEW COMMENTS ON THE PAST: IDEA FOR MAGIC WAS ‘BORN’ IN 1994/5 LARGE MIRROR INSPIRED BY A 17 m Ø SOLAR MIRROR OF THE DLR CONSTRUCTED IN LAMPOLDSHAUSEN MECHANICS INSPIRED BY THE DESIGN OF SCHLAICH, BERGEMAN AND SONS SOON OBVIOUS THAT THE ORIGINAL MIRROR CONCEPT UNSUITED FOR THE REQUIRED PRECISION OF AN IACT (FOCAL SPOT MUCH TOO LARGE) FUNDING AGENCY SET TIGHT PRICE LIMIT OF 5 MDM (=2.5 M€) IN 1996 SOME ORIGINAL GOALS • CLOSE THE ENERGY GAP BETWEEN 2. GENERATION IACTS AND EGRET -> THRESHOLD 15 GEV ? NOT POSSIBLE WITH CLASSICAL PMTS ->NEW DEVELOPMENT OF HIGH QE PMTS LOTS OF NEW PHYSICS EXPECTED IN THE ENERGY DOMAIN < 300(150) GEV • RECOMMENDATION FROM REVIEW COMMITTEE: BUILD MAGIC FIRST WITH CLASSICAL PMTS ALLOW FAST ROTATION FOR GRB OBSERVATIONS -> LIGHT WEIGHT CONSTRUCTION, RIGID CONSTRUCTION ALLOW OBSERVATIONS DURING PARTIAL MOON SHINE -> USE PMTS WITH LOW GAIN + VERY GOOD AC COUPLED PREAMPS INCREASE DAQ RATE TO 500-1000 HZ BUILD A NEW TECHNOLOGY TELESCOPE, AFTER SUCCESSFUL DEMONSTRATION -> MULTIPLE TELESCOPE (STEREO OR MULTIPLE PARALLEL OBSERVATIONS) WHY NOT A STEREO SYSTEM FROM THE BEGINNING ? NO FUNDING AGENCY WOULD HAVE GIVEN MONEY FOR 3-4 NEW TECHNOLOGY TELESCOPES WITHOUT TESTING A LARGE PROTOTYPE FUNDING AGENCIES WOULD FIRST REQUIRE 1 DEMO AND THAN DECIDE ON THE NEXT ONES. EVEN IF WE HAD APPLIED FOR NOVEL TELESCOPES WE COULD, WITHIN THE FINANCIAL LIMITS, ASK ONLY FOR SMALL TELESCOPES ADVANTAGE OF ONE LARGE TELESCOPE FIRST: LOWER THRESHOLD DISADVANTAGE: LOWER SENSITIVITY IN OVERLAP REGION LESSON TO BE LEARNED: IF THE CONSTRUCTION WILL BE TOO AMBITIOUS ONE WILL HAVE TROUBLE TO GET FULL SUPPORT FROM THE COMMUNITY (BMBF WAS MORE POSITIVE ABOUT NEW IDEAS AND NEW TECHNOLOGIES THAN COMMUNITY) THE MAGIC I TELESCOPE 17 mtr NOVEL OR UNCONVENTIONAL TECHNICAL COMPONENTS ITEM WHY . 17 m DIAMETER MORE LIGHT -OPTICAL DISTORTIONS SPACE FRAME - CARBON FIBER-EPOXY TUBES LOW WEIGHT, SEE LIST SINGLE MAST CAMERA SUPPORT LESS OBSCURATION, WEIGHT NEW MIRRORS LOW WEIGHT, CHEAPER, SEE LIST ACTIVE MIRROR CONTROL CHEAPER SPACE FRAME SPECIAL PMTS MORE SIGNAL, SEE LIST ANALOG SIGNAL TRANSMISSION OF PMT SIGNALS NO BULKY CABLES, SEE LIST 300 MHZ FADC NSB REDUCTION, NOW STANDARD OR EVEN OUTDATED MULTI-LEVEL TRIGGERS HIGHER TRIGGER SELECTIVITY NEW TECHNOLOGIES HAVE ALWAYS SOME RISK. GENERAL: 1 DEVELOPMENT ≈ BREAK EVEN OR FAILURE 2. PRODUCTION: REAL BREAKTHROUGH 3. PRODUCTION: SETS NEW STANDARD SOME TECHNICAL DETAILS I: CONCRETE FOUNDATION: CONVENTIONAL, WEIGHT >> TELESCOPE WEIGHT FOR STABILITY REASON: WIND, VIBRATIONS GOOD FOR 15 Y LIFETIME, BUT NOT FOR>>15 Y WE HAVE TO BUILD IN EASY DISMOUNTING KNOWN PROBLEMS: SHOULD BE WHITE TO PREVENT SUN HEATUP SHOULD BE BLACK TO SUPPRESS NSB REFLECTION DOME ?? TO EXPENSIVE BUT MAY BE NEW IDEAS AROUND TO COVER ONLY MIRROR RAIL: SIMPLE RAILWAY RAIL WITH < 1 mm VARIATION IN HEIGHT CURRENT SYSTEM CAN MOVE UNDER THERMAL EXPANSION SLIGHT DEFORMATION -> LIMITED TRACKING PRECISION RAIL SUPPORTED EVERY 60 cm -> SLIGHT DEFORMATION UNDER TELESCOPE LOAD (2 BOGEY WHEELS ≈ 210 CM APART->SOME EQUALIZING OF DEFORMATION BUT NOT ALL FOR 6 BOGEYS) NOTE: WITH 6 BOGEYS SYSTEM OVERDETERMINED_> SOME INTERNAL DEFORMATION OF SUBSTRUCTURE ->NO PERFECT SHAFTENCODERS NEEDED <-> PRECISE TELESCOPE AXIS POSITION MEASUREMENTS IMPOSSIBLE -> 13 BIT ENCODERS OK 0.02° LSB ALSO AFFECTING TRACKING: WE USE CHAINS LIKE IN A BICYCLE- SOME PLAY NOT PERFECTLY ROUND -> SOFTWARE CORRECTIONS NOT PERFECTLY SMOOTH (LINEAR) -ALSO A REASON WHY A PERFECT HIGH RESOLUTION SHAFTENCODER DOES NOT HELP NOTE: WE HAVE 1 SHAFTENCODER FOR AZIMUTH POSITION, 2 FOR DECLINATION (DEVIATE FROM EACH OTHER- MIRROR DISH DEFORMATION PROBLEM WITH CULMINATION-> SEPARATE TALK) TELESCOPE CAN TURN > 450° IN AZIMUTH -> MULTITURN SHAFTENCODER ENCODERS ARE ABSOLUTE ENCODERS -> NO CHANGE AFTER POWER FAILURE ENCODER ARE THE HIGHEST MECHANICAL PRECISION ITEMS OF DETECTOR DRIVE MOTORS: 11 KW SYNCHRO-MOTORS (CURRENTLY LIMITED TO ≈ 70% OF PEAK POWER) MAX TURNING OF TELESCOPE->CAN REACH 180° IN AZIMUTH IN ≈ 20 SEC 2 MOTORS FOR AZIMUTH (HAVE TO MOVE 64 TONS) 1 MOTOR FOR DECLINATION (HAS TO MOVE 22 TONS WEIGHT OF TELESCOPE ELEMENTS •BOGEYS 25.2 T •LOWER STRUCTURE 15.8 T •CAMERA 0.75 T •CAMERA MAST RING 1.2 T •MIRRORS 12. T •SPACE FRAME 5.6 T •COUNTER WEIGHT 2. T •AUXILIAR ELEMENTS 1.4 T •SUM ≈ 65 T LESSON TO BE LEARNED: BOGEYS ARE UNNECESSARY HEAVY, IF A BETTER SOLUTION FOR PROTECTION AGAINST STRONG WINDS CAN BE FOUND (SEE ALSO LATER COMMENT ON ADVERSE ATMOSPHERIC CONDITIONS) WHY DID WE CHOOSE A SPACE FRAME MADE FROM CARBON FIBER-EOPXY TUBES •LOW WEIGHT (5.4 TONS FOR MAGIC) •LESS DEFORMATION THAN STEEL OR ALUMINUM (17 MØ DISH QUITE DIFFERENT TO 10 MØ DISH ) •SAGGING ABOUT 1/2 OF SAME STEEL CONSTRUCTION •WEIGHT 1/3 OF STEEL CONSTRUCTION •THERMAL EXPANSION NEARLY ZERO •(STEEL EXPANDS BY 3 cm BETWEEN DAY-NIGHT TEMPERATURE CHANGE OF 50°C), WE SEE EFFECT VERY CLEARLY DURING DAY-TIME •HIGH OSCILLATION DAMPING •NO CORROSION-RUST DISADVANTAGES •HIGHER DEVELOPMENT COSTS (NOT MORE IN FUTURE) •HIGHER PRODUCTIOPN COSTS( NOW MARGINALLY HIGHER) •ORIGINALLY NO LONGTERM EXPERIENCE •LESSON TO BE LEARNED: RAPID PROGRESS IN CFRP CONSTRUCTION COMPONENTS. ENORMOUS PROGRESS IN YOUNGS MODULUS, MAX BREAKING LIMITS EPOXY MATERIALS MIRRORS ALL ALUMINIUM SANDWICH CONSTRUCTION WITH INTERNAL HEATING DIAMOND TURNED SURFACES, 10 DIFFERENT RADII (-> APPROXIMATION OF PARABOLA -> ISOCHRONOUS -> NO ADDITIONAL TIME SPREAD FOR SIGNALS STAGGERING- TIME SPREAD < 0.4 nsec) WE HAVE 49.5X 49.5 cm MIRROR ELEMENTS (DIAMOND TURNING TECHNIQUE 2000, OPTICAL DISTORTIONS SMALL) 4 MIRRORS MOUNTED ON A PANEL PANELS MOUNTED TO SPACE FRAM VIA AMC TOTAL MIRROR AREA 236m**2 MIRRORS HAVE QUARTZ COATING FOR PROTECTION ADVANTAGES: LESS WEIGHT THAN GLASS MIRRORS CHEAPER (WHEN USING WESTERN PRODUCTION COSTS) CAN HAVE NON-CIRCULAR SHAPE : SQUARES WITH ROUNDED EDGES… LESS DAMAGE DUE TO CORROSION EASIER TO PRODUCE WITH DIFFERENT RADII WILL NOT BREAK DISADVANTAGES SLIGHTLY LESS REFLECTIVITY CAN HAVE AGEING DEFORMATIONS DUE TO SLOW CONTINUING PLASTIC POLYMERISATION (MPI MIRRORS) CAN HAVE WATER LEAKS (DELAMINATION WHEN FREEZING) THE MIRROR COMPOSED OF 940 ELEMENT ALL ALUMINIUM CONSTRUCTION MANY DIFFERENT RADII (PARABOLIC PROFILE) Zur Anzeige wird der QuickTime™ Dekompressor “Foto - JPEG” benötigt. Mirrors quartz coated M. GARCZARZYK, USING METHOD PROPOSED. BY RAZMIK MIRZOYAN IN 2003 (SEE ALSO CONTR, PALAUSEAU CHERENKOV MEETING): OBSERVE DIRECT STAR + REFLECTED IMAGE ON CAMERA COVER VEGA, OBSERVED BOTH DIECTLY BY STARGUIDER CAMERA AND OVER CAMERA COVER (IMAGES OF VEGA COMPLETELY OVEREXPOSED) QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. THE ACTIVE MIRROR CONTROL FOR LARGE DISHES DEFORMATIONS A PROBLEM A)EITHER BILD A STIFF BUT HEAVY CONSTRUCTION B) OR A LOW WEIGHT CONSTRUCTION AND CORRECTION OF BENDING EFFECTS LARGE MODERN OPTICAL TELESCOPES FOLLOW B) MAGIC: THE FIRST TEST OF AMC FOR IACTS NO PREVIOUS EXPERIENCE INDUSTRY HAD NO SUITABLE UNITS AND WE HAD TO DEVELOP IT INHOUSE HARD ROAD TO GET IT WORKING PROBLEMS TO UNDERSTAND THE PRINCIPLE HARDWARE PROBLEMS WITH WATER TIGHTNESS IP67 NOT ENOUGH MONEY TO EQUIPP EVERY MIRROR WITH AMC BUT FINALLY IT WORKED WELL THE ACTIVE MIRROR CONTROL COUNTERACTS SOME SMALL DEFORMATIONS OF MIRROR SUPPORT FRAME EXAMPLE OF MIRROR FOCUSSED TO A LIGHT SOURCE 1000mtr AWAY PSF 0.03° AFTER MANUAL ADJUSTMENT (0.02° POSSIBLE) WILL DEGRADE DURING RUNS IF NOT FREQUENTLY READJUSTED pedestal 0.1° Slide 3 Lasers of the Automatic Mirror Control on a foggy evening … The camera Matrix of 577 PMTs Two sections: Inner part: 0.10 PMTs Outer part: 0.20 PMTs Plate of Winston cones Active camera area 100% SEE SEPARATE TALK FLORIAN GOEBEL A FREQUENTLY ASKED QUESTION WHY DID WE NOT BUILD A UNIFORM CAMERA TWO DIFFERENT SIZES OF PIXELS VERY INCONVENIENT MC, CALIBRATION, UNIFORMITY MAIN REASON WAS COSTS 1 PIXEL PRICE ≈ 2000€ AN ALL FINE PIXEL CAMERA WOULD BE NEARLY TWICE AS EXPENSIVE FINE PIXELS NOT JUSTIFIED FOR OUTER AREA DUE TO ABERRATIONS -> A POINT IMAGE BLURRED BY ABOUT 0.2° DUE TO f/D ≈ 1 + ALSO PARABOLIC PROFILE LESSON TO BE LEARNED: USE f/D > 1.2 AND AT LEAST 5° FOW CAMERA WITH UNIFORM PIXELS IF MONEY IS NOT THE MAJOR CONSTRAINT A PARABOLIC PROFILE IS NEARLY A MUST WE USE HEMISPHERICAL PMTS WITH 6 DYNODES ADVANTAGES •BETTER TRANSIT TIME SPREAD •OPTIMAL FOR LIGHT CATCHERS •SOME DOUBLE CHANCE OF PHOTON-PHOTOELECTRON CONVERSION •LOW GAIN-> LOW ANODE CURRENT DUE TO NSB, MOON SHINE-> •LESS AGING, LESS DAMAGE, CAN WORK DURING MOON SHINE •LESS POWER FOR HT, LOWER HT, LESS BLEEDER CURRENT-LOWER HEATING IN CAMERA •FASTER •HIGHER GAIN FOR PANEQUE LACQUER ->ABOUT 13-15% PHOTON-PHOTOELECTRON CONVERSION POSSIBLE DISADVANTAGES HIGH QUALITY PREAMP NEEDED CAN HAVE MORE PICKUP, NOISE ON SIGNAL OTHER DISADVANTAGE SPECIFIC TO SELECTED PMT HIGH AFTERPULSE RATE AND LARGE AFTERPULSES FOR HIGH PE COLLECTION EFF. TUBE VACUUM WE HAVE A CAMERA WINDOW THAT CAUSES 8% LIGHT LOSS WE HAVE SOME PROBLEMS WITH TEMPERATURE STABILIZATION, HUMIDITY ONE GENERAL ISSUE IF ONE USES PMTS:WHAT IS THE PHOTOELECTRON COLLECTION EFF. Zur Anzeige wird der QuickTime™ Dekompressor “Foto - JPEG” benötigt. CAMERA Gain: Wiston cone + Laquer coating ----- cone lined with 3M dielectric foil + laquer coating ----- cone lined with aluminised Mylar + laquer coating ----- plain PMT, diaphragm 22 mm RELATIVE GAIN/cos , NORMALIZED TO 0° INCIDENCE OF PLAIN PMT 3 <- LIMIT ANGULAR ACCEPTANCE -> 2,5 2 1,5 AREA RATIO OF Winston Cone/PMT=1.91 1 0,5 0 -60 -40 -20 0 20 ANGLE OF INCIDENCE 40 60 PM GAIN ≈ 10 000 PM type 9116A NOTE: NON-NEGL. SENSITIVITY TO NSB LIGHT SCATTERED FROM GROUNG CONNECTION BETWEEN CAMERA AND DAQ MAGIC USES OPTICAL FIBERS FOR THE ANALOG SIGNAL TRANSFER FROM CAMERA PMTS TO THE 100 M AWAY COUNTING HOUSE PROS: LOW WEIGHT OF CAMERA (OSCILLATIONS REDUCED) REDUCED ELECTRONICS IN CAMERA -> LESS DOWNTIME DUE TO DEFECTS LOW POWER CONSUMPTION IN CAMERA EASIER TO MODIFY ELECTRONICS (TRIGGER…) EASIER TO IMPLEMENT TRIGGER FOR MULTITELESCOPESYSTEM CONS: NEW PRINCIPLE, NO EXPERIENCE EXTRA COSTS USE OF VCSELS AS LIGHT EMITTER (CAN DRIVE TO 200 MA PULSE CURRENT FOR LOW DUTY CYCLE. HIGH BANDWIDTH (> 1 GHZ POSSIBLE, NOW 230 MHZ BW) NO ATTENUATION OVER 165 M LENGTH ACHIEVED DYNAMIC RANGE ≈ 800 (LINEAR), > 1000 WITH SOME NONLINEARITY WE ARE WORKING ON NEXT GENERATION ‚MONOMODE‘ VCSELS. -> HIGHER STABILITY, LOWER NOISE, LOWER POWER EXPERIENCE WITH ADVERSE ATMOSPHERIC CONDITIONS HIGH WIND SPEED, GUSTY WINDS •NO PROBLEM TO OBSERVE AT WINDSPEEDS > 10, BUT < 15 m/SEC WIND •CAMERA OSCILLATIONS VERY SMALL •CFRP TUBES HIGH OSCILLATION DAMPING (PROBLEMS WITH LONG METAL TUBES) •USE OF HEAVY BOGEYS: A SAFETY ISSUE BUT BETTER SOLUTIONS WITH MUCH LESS WEIGHT POSSIBLE •HIGHEST WIND SPEED AT SITE UP TO NOW ≈ 140 KMH -> NO PROBLEMS HUMIDITY: SERIOUS PROBLEMS BECAUSE NOW MORE ELECTRONICS, ELECTRICAL COMPONENTS… A LESSON TO BE LEARNED: COMPONENTS MUST BE IP67 TESTED FOR LONG DURATION AND STRONG SUN LIGHT EXPOSURE ICE, DEW: LESS SERIOUS THAN ANTICIPATED: HEATING OF MIRRORS WORKS BUT POWER CONSUMPTION MIGHT BE A PROBLEM UV-LIGHT OF SUN (CAN BE VERY DESTRUCTIVE AT HIGH ALTITUDE FOR PLASTICS) NO SERIOUS PROBLEMS ENCOUNTERED (EX CABLE BINDERS…) FAILURES OF ELECTRICAL POWER CAN BE A PROBLEM FOREST FIRES CAN BE A SERIOUS PROBLEM LIGHTNING PROTECTION FAST PM SIGNAL TRANSMISSION BY OPTICAL FIBER SYSTEM WORKING IN ANALOG MODE VCSEL PM, 6 DYNODES PIN PHOTODIODE OPTICAL FIBER 160 mtr TO TRIGGER LOGIC TO FADC . AMPL PREAMP •VERY LOW FAILURE RATE AFTER ≈ 1 YEAR •VERY LOW CROSSTALK, NO PICKUP •LARGE DYNAMIC RANGE (>60 db) •SOME NONLINEARITY •SOME GAIN SHIFT AND MODE HOPPING •NEEDED TO SELECT VCSELS Input pulse ≈ 2.5 nsec Output pulse at optical fiber system, 160mtr Output pulse after RG 58C cable, 156 mtr SUMMARY MANY TECHNOLOGIES USED IN MAGIC WERE VERY AMBITIOUS IN 2000 BUT NOW NEARLY ‘CONSERVATIVE ‘ CAMERA AND ELECTRONICS ARE OUTDATED MOSTLY AFTER 4-6 YEARS (WE HAVE PROBLEMS TO GET SOME SPARE ELECTRONICS CHIPS) EXAMPLES 300 MHZ FADCs, FAST COMPARATORS THERE ARE ALSO NEW SOLUTIONS FOR HARDWARE STRUCTURE AVAILABLE FOR LARGE DISHES FOR REASONABLE COSTS HIGH WIND SPEED MIGHT BECOME A PROBLEM MORE AND MORE ELECTRONICS COMPONENTS - PROBLEMS WITH WATERTIGHTNES SERVICING AND REPAIR VERY GOOD EXPERIENCE (EXCEPTIONS CONFIRM THE RULES) WITH DIAMOND TURNED MIRRORS AMC A VIABLE SOLUTION TO BUILD LOW WEIGHT DISHES The Calibration: hardware • Nishia single quantum-well LEDs • Light pulses in 3 colors (UV, blue and green) • Different intensities over dynamic range of factor 300 • Match pulse width of cosmics • Trigger available over wide range of frequences: E.g.: - Calibration run: 500 Hz - Data run with interlaced calibration events: 50Hz - Test runs up to: 4 KHz WE HAVE A TEMPERATURE STABILITY PROBLEM SOME KEY MAGIC PARAMETERS: •MIRROR AREA 242 m2 f/D = 1 MIRROR Ø: 17 m MIRROR PROFILE: PARABOLIC (ISOCHRONOUS) •MAIN MIRROR COMPOSED OF 940 ELEMENTS, •ALL ALUMINIUM SANDWICH UNITS, DIAMOND TURNED, LIGHTWEIGHT, HEATEABLE •ACTIVE MIRROR CONTROL TO COUNTERACT SMALL DISH DEFORMATIONS •574 PIXEL CAMERA, 3.5 ° Ø, INNER PIXELS 0.1°Ø, OUTER PIXELS 0.2° Ø, SPECIAL LIGHT CATCHERS •HEMISPHERICAL PMTS (ET 9116,9117, 6 STAGTES) TREATED FOR ENHANCED QE (30-34% AT PEAK l) • LOW LOSS, HIGH BW (> 250 MHz) SIGNAL TRANSMISSION BY OPTICAL FIBER SYSTEM •THREE LEVEL TRIGGER (REJECTS ALREADY A FRACTION OF HADRONS ON TRIGGER LEVEL) •TRIGGER AREA ≈ 2° Ø, TRIGGER RATE 250-300 Hz ( TECHNICAL LIMIT 1 KHz) •SIGNAL DIGITISATION: DUAL RANGE FADC (≈ 58 dB DYN. RANGE) , DIGITISATION FREQUENCY 300 MHz •MAX ROTATION SPEED: 23(20) sec FOR 180° TURN -> FOR RAPID RESPONSE TO GRBS(CONTROLLED •TESTS), CURRENTLY NO REVERSE MODE -> SOMETIMES 360° TURNS NECESSARY, ALSO SLOWER •BECAUSE OF SAFETY REASONS SOME KEY MAGIC PARAMETERS II: TRACKING PRECISION ≈ 0.02 (WITHOUT STARGUIDER CAMERA) EXPECT TO REACH 0.005 WITH STAR GUIDER CAMERA PSF: 0.03° EXPECT TO REACH 0.02° FOR OPTIMISED AMC CURRENT THRESHOLD: AROUND 50 GeV (TRIGGER) AROUND 80-90 GEV FOR PHYSICS ANALYSIS ->30-40 GEV FOR SPECIAL PULSAR TRIGGER CURRENT SENSITIVITY: STILL ABOUT FACTOR 2-3 WORSE THAN PREDICTED (USE OF CLASSICAL IMAGE ANALYSIS NOT SO EFFICIENT < 150 GeV) Maximizing Double-Hits in a PMT PMT Not yet optimized for the milky PMT coating Significant additional improvements to come OLD TRICK OF ASTRONOMERS TO INCREASE QE SMALL PRISM PHOTOCATHODE A TOY MODEL MOST LIGHT TRAPPED INSIDE HIGH n MATEREIAL FRACTION OF LIGHT SCATTERED OUT GRADED DIFUSSE SCATTER LAYER WITH MICROSCOPIC VOIDS PHOTOCATHODE