1. Brenda Dingus 2 June 2005 Using Multiplicity Scalers to Constrain Solar Spectra Low Threshold of Air Shower PMTs have 8 different multiplicity discriminators (~6.25 mV/PMT) which we monitor with the EMS CAMAC scalers I recently measured the discriminator thresholds to be 4, 6, 10, 11, 19, 29, 34 (i.e. not 4, 8, 12, 16, 25, 32, 40) These rates have historically been very sensitive to crate temperature. I added AC couplers before each discriminator which improved temperature stability greatly. (Apparently the DC offset of the linear fan in/out varies with temperature.) However, there is still an overall offset due to the high singles rate that has not yet been quantified.

2. Brenda Dingus 2 June 2005 Effective Area Monte Carlo Tony Shoup’s memo of 3/16/05 details effective area energy for 8 multiplicity thresholds. Used GEANT3 and GHEISHA. Fit effective area to a power law function I fit the 2 parameters as a function of multiplicity using a linear fit for Ao and a quadratic for p. For a power law source function, then the rate for a given multiplicity i is

3. Brenda Dingus 2 June 2005 Effective Area vs Multiplicity

4. Brenda Dingus 2 June 2005 Check Against Cosmic Ray Rate Use BESS data as given in Tony’s memo and measure rates with scaler at site by hand (i.e. not very accurate).

5. Brenda Dingus 2 June 2005 Percent Change in Rates due to Source E -2 E -4 E -3 E -8

6. Brenda Dingus 2 June 2005 Percent Change in Rates for Different High E cut offs E -2 E -4 E -3

7. Brenda Dingus 2 June 2005 Observed Scaler Increases Tony’s Brightest Scaler Increases 20 Jan 2005 Solar Energetic Particle Event

8. Brenda Dingus 2 June 2005 What Next? Get normalization of spectrum at a few GeV for the 20 Jan 2005 event from Climax Neutron Monitor GEANT4 & Fluka change effective areas at low E (see Tony’s talk) Study zenith angle dependence Try to quantify stability of scalers Study triggered events to see variations in multiplicity Consider different quantities to scale More CAMAC scaler channels appear to be available Only use top tubes now Bottom tubes are better indicators of muons Could use patches on top and bottom layer to get directionality