SNDICE SuperNova Direct Illumination Calibration Experiment

SNDICE Calibration Instrumentale de Megacam Installation au CFHT fin 2007 (durée > 1 an) Collaborateurs : –P. Bailly, E. Barrelet, W. Bertoli, C. Evrard, J-F Huppert, C. Juramy (  2006), H. Lebolo, K. Schahmaneche, R. Sefri, A. Vallereau, D. Vincent, Coût total  125 k€

Revue SNDICE 13 Novembre 2006 Conseil scientifique 24 Novembre 2006CSP 12 Décembre 2006

Illumination Directe source de LEDs calibrée (LPNHE ) Monitoring du telescope Echantillonage de R( ) Design simple

Banc de test actuel

Mesures prévues sur le banc de test LEDs : –Obtenir une lumière stable avec contrôle du courant et du photocourant dans photodiodes de contrôle –Relations entre tension, courant, température, et puissance lumineuse émise –Distribution spectrale –Distribution spatiale : Integral Radiometric Calibration CLAP : –Mesure et amplification de signaux qq fA/cm 2 –cross-calibration avec photodiode calibrée NIST, via la calibration des LEDs  Prototype d’une carte avec 8 voies (Janvier 2007)

Workpackages  Électronique de contrôle et acquisition  Asic  Tête de LEDs  Banc de calibration

Schéma du dispositif (Cooled Large Area Photodiode) (LEDs source)

Carte électronique principale Précision visée : < 1 ‰ Sources de courant des LEDs : 20 DACs 12-bit, 20 switches, un temps de pose commun Lecture du courant des photodiodes : LCA, multiplexeur, ADC 16-bit Alimentations pour : DACs, ADCs, LCAs, polarisation des photodiodes FPGA Ethernet : XiLinks Virtex 4 pour la programmation du FPGA to LED source DACs to computer LCAs MuxADC FPGA

Photodiode refroidie (CLAP : Cooled Large Area Photodiode)  Mesure redondante  qq fA/cm 2  refroidissement (Peltier)  “grande” surface  besoin d’un LCA (Low Current Amplifier) SNDICE – LCA

LCA : schéma SNDICE – LCA

ASIC (R&D SNAP)  préampli de courant  ampli de tension double gain SNDICE – LCA

SNDICE – Tête de LEDs Specifications 1. LEDs module  Design of the LEDs module as much for the test bench as for the installation on the telescope Requirements (although specifications are not precisely defined yet) : Number of LED : between 20 and 24 (to cover spectral bandwidth from UV to NIR)  surface mount form factor LED with flat top 1 control photodiode associated with every LED  could be edge-illuminated photodiode ? Baffling against stray light  1st mask to get rid of rim reflection so that we have an almost point-like light source  2 nd mask acting as a diaphragm to get a cone shape light with an angle of 3° Constraints from climate and weather environnement at CFHT Space requirements to stay outside telescope and camera field of view Interface with telescope structure for fastening Equipped with a sight system and tilt-and-swivel mechanism to adjust the optical axis toward the camera

SNDICE – Tête de LEDs Fixation and positionning of the LEDs  our previous experience : home-made mechanical positionning, LED glued Requirements  better to use industrial electronic means and solder LED directly on an PCB ?

SNDICE – Banc de calibration  2nd step : calibrate the LEDs by using the NIST calibrated photodiode The aim is to define a 3D map of the light field and measure light homogeneity for each LED within an useful area  we need to move either the light source or the light receiver relatively to each other with 3 degrees of freedom  The distance between source and receiver would range from 1m to 2.5m to get adequate illumination  3rd step : calibrate the Hamamatsu photodiode with the then calibrated LEDs We need to increase the distance between source and receiver to lower illumination In order to come close to working conditions on the telescope, this distance should be around the focal plane distance of Megaprime (~13.5 m)  extension of the optical bench  4th step : design for the lay out of the calibrating system on the Megaprime instrument  1st step : test of LEDs and photodiodes to choose the right ones  prototypes of LEDs module

SNDICE – Banc de calibration LEDs module Photodiodes 1 NIST calibrated photodiode (high illumination sensitivity) 1 Hamamatsu cooled photodiode (low illumination sensitivity) Optical bench Black box (not drawn)

SNDICE – Banc de calibration Specifications 2. Optical bench Motorized translation along the optical axis (Z) scanning 1m to 2.5m from the LEDs module precision : 0.5 mm (enough to be precise better than 0.1% related to the distance) XY motorized translation system scanning an area around 20x20 cm² precision : 0.5 mm Tilt-and-swivel system to align LEDs and photodiodes precision : fraction of milli radian existing granit rail existing XY translation system ? Carriage guided by 4 rollers along aluminium profil motor driven by synchronous belt repeatability +/- 0.1 mm Black box - Feedthrough for power and signal cables - Opening on one side to « extend » the bench up to 14m

Schedule (1)

Schedule (2)

Schedule (3)

Manpower 3.4 h*ans 2.4 h*ans 0.2 h*ans Total = 8.9 h*ans 2.9 h*ans

Cost

DICE Group Review Findings (Paris Nov 13, K. Gilmore invited) Photometric calibration is indeed a key issue of current and future wide field surveys Quantify the scientific gain Direct illumination with LEDs is a very appealing concept Key features (stability and control, LED light emission properties, …) to be validated on test/calibration bench Get results from «Dome illumination with a tunable laser » experiment at CTIO (C. Stubbs) Cost estimate found ok - Technical team found strong Problem with the leaving of C. Juramy in Jan 07 Go forward: immediately - do test/calibration bench validation measurements - start discussing implementation with CFHT

Risques (1) Accord du CFHT ? –Courrier au CFHT cet été –Une visioconférence fin Novembre –23-11: CFHT prêt à collaborer à cette étude –Envoi d’un proposal au CFHT le –Une visioconférence avant la fin de l’année –…

Risques (2) Choix des leds –Mesures sur le banc test en cours –…

Risques (3) Ressources –Budget réaliste –Manpower ITA, pas de problème –Départ de Claire Juramy fin Décembre Mesure sur banc test Analyse

Conclusions  Peu de problème, mais:  Encore beaucoup de mesures, de tests et de simulation à faire : MANPOWER côté physiciens  Si validé : calibration pour des expériences ultérieures (LSST, satellites,…)