Sky Background Measurements at Los Leones

Transcription

1 Sky Background Measurements at Los Leones C.B.Bonifazi 1,3, D.V.Camin 6, P.F.Gomez Vitale 4, V.Grassi 6, M.Lantz 3, M.Lapolla 6, M. Santander 2,5, M.Santarrosa 2,5, A.Risi 2,5, D.Rodriguez 3, V.Scherini 6, G.Sequeiros 5 1Laboratorio Tandar, CNEA 2Museo de Ciencias Naturales de San Rafael 3Universidad Nacional de Buenos Aires 4Universidad Tecnologica de Mendoza 5Universidad Tecnologica de San Rafael 6Universita di Milano/INFN

2 Instrumentation Two PMT s XP Head Electronics High resolution volmeter HP GPIB bus Lab View software driver + DAQ on laptop Telescope with 15 cm diam. mirror f/8 MUG2 and HiRes UV Filters Measurements done at : Buenos Aires (Top of Tandar Lab building) San Rafael (Observatory of Natural Science Museum) Auger site, at Los Leones

3 Targets A star (Alfa Centauro)and its nearby background in three different places: BsAs, SR, Los Leones Background, looking NO at Los Leones Zenit with the telescope and with an open PMT.

4 Scaling our measurements to actual FD size Auger: FD mirror area camera area = 3 m 2 Aperture 2.25 deg 2 Telescope: Mirror area = m 2 Aperture 2.34 deg 2 Scaling factor: 163

5 Scaling the directly exposed PMT 103 deg PMT+HE Photocathode area : m 2 Scaling Factor : 3m 2 x str / m 2 / 2.37sr SF= FD/PMT = 0.85

6 Square wave on LED illuminating the PMT V out [V] 0.5mV/div phel/100ns=56fa Time [sec]

7 Preliminary measurements at Torino Astronomical Observatory The following measurements were taken at Pino Torinese Astronomical Observatory using the 1.05 m REOSC telescope. The two graphs show the different response of the PMT to orange, white and blue stars. FILTER WHEEL PMT Telescope data: primary mirror diameter 1050 mm focal lenght 9943 mm image scale 20.7 arcsec./mm linear obstruction 60%

8 The UV filter was provided by the observatory in the filter wheel, it is a U band filter from the UBVRI system made of 3 filters superimposed. The spectral response is given below. trasmission U filter UG1 BG18 WG225 Total nm

9 Pino Torinese no filter 1.0 Relative mag.= 2.5log(i/i 0 ) i 0 : PMT current from Vega relative magnitude (Vega=0) Star spectra: blue (B) white (A) orange (K) red (M) Visual magnitude Note that the departure from the straight line is due to the higher weight of the background for fainter stars.

10 Pino Torinese U filter 1.00 A0 relative magnitude (Vega =0) B3 A0 B5 A0 Star spectra: blue (B) white (A) Visual magnitude Orange and red stars give too low signals to be measured

11 Preparing Telescope, PMT and Filter adapters, etc...

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14 Alfa Centauro MUG2 Filter Los Leones Telescope Measurement V out [volt] 1 mv/div Star ( phel/100ns = 405 fa) Background (0.044 phel/100ns = 70 fa) Time [sec]

15 Alfa Centauro MUG2 Filter Los Leones Signal scaled to Auger V out [volt] Dark level Background Star Time [sec]

16 Alfa Centauro HiRes Filter Los Leones V out [volt] 1mV/div Background (0.039 phel/100ns = 62 fa) Star (0.252 phel/100ns = 403 fa) Time [sec]

17 Zenit MUG2 Filter Los Leones PMT directly exposed V out [volt] Background (10 phel/100ns) Auger scaled: 8.5 phel/100ns No Filter Time [sec]

18 MUG2 Filter Alfa Centauro and Background Different places Los Leones San Rafael Buenos Aires V out [V],0.58 phel/100 ns/ div Time [sec]

19 Results scaled to Auger FD prototype [phel/100 ns] Alfa Centauro Background Without Filter MUG2 Filter HiRes Filter Mean Sigma Mean Sigma Mean Sigma Buenos Aires San Rafael Los Leones Background Without Filter MUG2 Filter HiRes Filter Mean Sigma Mean Sigma Mean Sigma Buenos Aires San Rafael Los Leones: near αcentauro Zenit NO, 30 deg open PMT to Zenit

20 Background results scaled to Auger FD prototype [ph/µs/m 2 /deg 2 ] ( quantum efficiency = 20 %) conservative value Without Filter MUG2 Filter HiRes Filter Mean Sigma Mean Sigma Mean Sigma Buenos Aires San Rafael Los Leones: near αcentauro * Zenit NO, 30 deg 51 * open PMT to Zenit *) Most significative values for Auger. 30 % larger than HiRes 40 ph/us/m2/deg2. 14 % larger noise.

21 Background results scaled to Auger FD prototype [ph/µs/m 2 /deg 2 ] ( quantum efficiency = 25 %) acccording to Philips data sheet Without Filter MUG2 Filter HiRes Filter Mean Sigma Mean Sigma Mean Sigma Buenos Aires San Rafael Los Leones: near αcentauro * Zenit NO, 30 deg 41 * open PMT to Zenit *) Most significative values for Auger. confirms HiRes 40 ph/us/m2/deg2 also for the southern site.