Radiation Units Radio Telescope Geoffrey Lovelace 04/13/01

Radiation Units n Physical Units – Roentgen (R) (oldest) n amount of radiation to produce 2.58*10 -4 C / kg charge on ions of one sign in dry air s.t. freed electrons are all stationary. – All energy of radiation spent in freeing electrons n 1 C/kg = 3880 R n Used for X-rays below 4 MeV Source for units information: Penguin Dictionary of Physics (1977).

Radiation Units n Physical Units – Becquerel n Amount of radioactive sample s.t. there is 1 atomic decay per second n Henri Becquerel: discovered radioactivity through experiments with uranium and other radioactive matter – Curie (Ci) n 3.7*10 10 decays per second n Approx. activity of 1g radium

Biological Units n Gray (Gy) n Amount of radiation s.t. 1 kg of tissue absorbs 1 J of energy n Rad (rad) n Radiation Absorbed Dose n.01 Gy; amount of radiation s.t. 1 g of tissue absorbs 1 erg (10 -7 J) n Relative Biological Effectiveness (RBE) – Radiation effectiveness varies with type n Particle radiation tends to damage tissue more than X-Rays or Gamma Rays

Biological Units n Sievert (Sv) – Radiation in Gy multiplied by an RBE scaling factor – 1 Sv approx. 1 Gy for gamma rays (RBE=1) – Rolf Sievert: Swedish physicist, first professor of the Dept. of Medical Radiation Physics in Stockholm

Biological Units n Rem (Radiation-Equivalent Man) – 1 Rem = 100 Sv=1 rad * QF – QF = Quality Factor (Acts as RBE) – QF = 1 for gamma, high energy beta – QF = 1.8 for low energy beta, QF=10 for neutrons n Smaller Units – Sv, rem can be too large – More common: mSv, mGy

Works Consulted n n Pitt, Valerie H., Ed. The Penguin Disctionary of Physics. n ert.html

Telescope Update – Heterodyning Unit Completed n Punched holes for BNC voltage supplies, ground – For +12V, +15V, and V supplies n Soldered connecting wire for ground, voltage n Completed cable connection between oscillator and attenuator – SMA Male to SMA Male (Connector Type) – RG-58 coax cable (specify R=50 Ohm and thickness) Cut as shown, attach connector, and crimp 1/8” center only 1/4” shield+ins.+center Sheath Shield Insulator Center connector RG-58 cut positions

Telescope Update – First Test: Receiver, Heterodyning Unit – VCO correctly subtracts a variable frequency from the RF Signal – ~ 4 GHz RF from heterodyning unit detected n Source Uncertain n Metal case blocks this signal – Next Steps n Run Cable, Mount Receiver on Dish n Prepare computer software for FFT