A high pressure discharge lamp includes a quartz glass bulb and a pair of electrodes.
Each electrode of the pair of electrodes is disposed so as to be opposite the other
in the quartz glass bulb. The quartz glass bulb of the high pressure discharge
lamp contains at least mercury and a halogen gas which are airtightly sealed in
the quartz glass bulb. The partial pressure of oxygen (O) in the quartz glass bulb
is about 2.510-;3 Pa or less and the partial pressure of the halogen
gas in the quartz glass bulb is in the range between about 110-;6 mol/mm3
and 110-;8 mol/mm3. The pair of electrodes
contain potassium oxide in the range between about 20 ppm and 40 ppm.
