Sistema di distribuzione laser C.Ferrari, A.Fioretti, C.Gabbanini, G.Venanzoni INO, UOS Pisa, Via G. Moruzzi 1, 56124 Pisa LNF, INFN Frascati

Outline: Schema baseline finale Stato del pannello Sistema baseline: motivazioni scelta diffusore (vs. sfera) Schema baseline finale Stato del pannello Test stabilità catena di distribuzione Budget energia Conclusioni

Risposta temporale: Sfera Diffusore Uniformità spaziale: Sfera Diffusore ~ 1-2% regolabile (> 2-3%) Trasmittività: Sfera Diffusore ~ 1% regolabile ~ 10% (tot.su bundle fibre 1mm) (tot.su bundle fibre 1mm)

Uniformità spaziale / Trasmittività with lens sphere no lens no lens

Diode Laser from Picoquant Multilaser 8 channel sepia LDH-P-C-405M A crate+driver+1 head arrived Wavelength: 405 nm ± 10nm Pulse FWHM: < 700 ps Average Power (@ 40 MHz): 28 mW Power stability 12h, DT < 3K: 1 % RMS, 3 % p to p Measured light output: 1000pJ/pulse @ 10 kHz

Schema baseline PANEL X 24 Laser hub Calorimeter RING Laser control f Local Monitor DAQ, Slow Control Calorimeter Fiber collimator 50/50 Fiber bundle Laser control Source Monitor Launching fiber Diffuser filter wheel Local Monitor laser1 T80/R20 50/50 50/50 laser2 X 24 laser3 laser4 laser5 laser6 RING Laser hub

Pannello PMMA fiber Prism PbF2 crystal SiPM

Distribuzione luce in uscita dai cristalli Fibra 1mm PMMA NA=0.49 Disomogeneità 3% integrata su 12 mm (dimensione SiPM)

Misura della trasmissività della linea di distribuzione con power meter

Distribution system transmission: 6 lasers/ 24 diffusers Element Transmission Energy (pJ) Notes Laser Picoquant output 1000 100% current intensity Source monitor sampling 80% 800 200 pJ/pulse for the source monitor (2 PD and 1 PMT) Filter wheel 100%   Division into four fibers 25% 200 Fiber coupling + 25 mt quartz fiber 160 Measured Diffuser with bundle (54 fibers) + 3 local monitors 10% 16 It can increased by reducing uniformity 1 mt bundle POF (200 dB/km) 90% 14.4 Prism coupling 65% (1stmeasure) 9.4 Prism with anti-reflection coating and with metallized reflecting face PbF2 crystal reflection + absorption (20%) 6.0 without optical grease we expect 75% Total per calorimeter Required: 0.6 pJ /pulse /calorimeter Distribution system transmission: 6 lasers/ 24 diffusers Required value of the output of each crystal: 0.01 pJ/pulse; for each calorimeter: 0.6 pJ/pulse

Energia in eccesso utile per processo calibrazione SiPM

Stability of distribution system (a few pJ/pulse at the PINs) diffuser PIN2+CREMAT CAEN DT5730B Laser launching fiber (f=600 mm) PIN1+CREMAT Fibers PMMA 1mm sistematico ~ 4 10-4/h

Conclusioni Lo schema con 6 laser e 24 diffusori è un ottimo compromesso per: energia ai SiPM stabilità sostenibilità dei costi modularità approvazione degli americani In corso di progettazione e realizzazione un prototipo di catena completa di distribuzione (dal laser al pannello baseline) per portare al test beam (gennaio a SLAC?) o a Seattle

SPARES

Diffuser Engineered diffuser ED1-C20 by RPC Photonics – sold by Thorlabs

Transmission coefficient- sphere Fibers are grouped in two classes with different transmission This is due to the bundle and not to the sphere: infact, by changing port for the bundle, the behavior is unchanged The transmission coefficient among the two groups differs by 10%. Within each group just by 2%. The transmission coefficient is: Ti = (1.01 ± 0.03)· 10-5 or Ti = (0.91 ± 0.03)· 10-5

Transmission coefficient- diffuser Measurements with/without collimating lens changing the distance diffuser-bundle or lens/bundle Inhomogeneity strictly connected with transmission coeff.

Transmission coefficient- diffuser with lens sphere no lens Inhomogeneity strictly connected with transmission coeff. Best results: without lens 5.7% in a bundle group T=1.5 10-4 (new with square pattern diffuser: 4%) with lens 7% in a bundle group T=2.4 10-4

Light uniformity map Pulsed laser Nd:YAG, l = 532 nm, 20 Hz repetition rate, 10 ns pulse width; model: Continuum Surelite I-20 Pentax camera (mod. K100D), with a short shutter time (1/30 s) to acquire a single shot Sphere: camera acquires radiation coming from a specific portion of the sphere inner surface. Diffuser: camera without lens placed instead of bundle

Sphere Data averaged over 900 pixels (1mm): Uniformity of the order of 0.982, in the central part up to 0.993.

Diffuser no lens 2% inhomog. on 0.2 mm in the central zone with lens