TEST BEAM A SLAC Time relative to beam

TEST BEAM A SLAC Time relative to beam entry P. W. Gorham et al. . shower nearly dissipated Antenna V/Vrms 6 GHz bandwith oscilloscope Antenna V/Vrms close to shower maximum Time relative to beam entry

TEST BEAM A SLAC sensitive to cherenkov and transition radiation 7 ns decay constant, compatible with plasma cooling P. W. Gorham et al. . insensitive to cherenkov and transition radiation classical bremsstrahlung theory assuming coherence

THE AMY OBJECTIVE Limitations of SLAC measurements It has been proved only the existence of a microwave emission • the absolute yield is not known precisely --> this affect the uncertainty on the threshold in energy of an air shower detector • the spectrum in frequency has not been measured --> it may give important informations on the underlying process --> if there are bright lines the signal/noise of a telescope can be improved --> if not, satellite televisions band are preferable to keep low the costs With the AMY experiment we would like to overcome this limitations confirming and measuring precisely the absolute microwave yield and its frequency spectrum in the range between 1 and 25 GHz

The DAFNE Beam Test Facility e-/e+ Energy range 25 -750 Me. V Max. repetion rate 50 Hz Pulse duration 1 - 10 ns Particles/bunch Up to 1010 In comparison to SLAC the BTF beam provides a larger shower equivalent energy

ANECHOIC FARADAY CHAMBER 2 antennas beam axis 2 m RF adsorber SATIMO AEP 12 attenuation 1 GHz: 30 d. B > 6 GHz: 50 d. B 2 m copper 4 m 30 cm choice of dimensions • far field approximation (-> height and width) • entrance and exit walls outside the antenna field of view (-> length)

ANECHOIC FARADAY CHAMBER 2 antennas beam axis 2 m 2 m 4 m • spectrum analyzer -> frequency spectrum and absolute yield • power detector & FADC (*) ->time evolution of the signal (*) flexibility of a VME system (beam monitoring)

EXPECTED FLUX DENSITY at the maximum energy deposit within the chamber assuming an alumina target beam-antenna distance alumina target observed track lenght depends on the degree of coherence = 1÷ 2 alumina target

THE ANTENNA Rohde & Schwarz HL 050 Log-periodic 0. 85 -26. 5 GHz 27. 4 cm from 1 to 25 GHz Half-power beam width 650 -> 550 Cross-polarization factor 40 -> 35 d. B

SPECTRUM MEASUREMENT Spectrum analyzer Rohde & Schwarz FSV 30 9 KHz - 30 GHz 40 MHz bandwidth amplifier ANTENNA Gampl ≈ 25 d. B

SPECTRUM MEASUREMENT Spectrum analyzer amplifier ANTENNA Expected signal at the maximum energy deposit quadratic scaling bandwidth amplifier antenna effective area linear scaling well above the expected instrumental noise (< -80 d. Bm)

TIME MEASUREMENT FADC power detector amplifier ANTENNA AD 8317/8318 500 MS/s 12 bit resolution 4 channels up to 10 GHz response time < 10 ns (no signal -10 d. Bm)

TIME MEASUREMENT FADC power detector amplifier ANTENNA Constraints from power detector • difficult to go above 10 GHz • minimum signals > -60 d. Bm Measuring the exponential decay with a 30 -40 d. B dynamic range high amplification gain 1) perform an initial measurement around a fixed frequency (commercial feeds in satellite bands) 2) once the spectrum has been measured, study the time signal evolution in the bands we will find interesting (above 10 GHz we may use frequency down converters) C band

Cherenkov electric field - 1 e-

Cherenkov: no target - quadratic scaling density flux at the end of the camera after the adsorption (50 d. B) density flux at the antenna cross -polarized (40 d. B) MBR density flux at the antenna maximum shower development

For a realistic calculation: • time separation between electrons coherence only if t << 1/f (0. 04 ns < 1/f < 1 ns) 1 ns < bunch duration < 10 ns • only particles within the chamber contribute to the signal • modelling RF absorption

Dealing with 1010 particles Expected cherenkov signal in the spectrum analyzer in case of a copolarized antenna > -10 d. Bm An import goal of the test beam will be to measure the cherenkov radiation and to make a comparison with theoretical calculations

Agilent (? ) The experiment has been fully funded by INFN (~ 120 k€) and some of the instrumentation will be bought already during this year.