Questions & Answers


Talk by Vsevolod (Seva) Souvorov

	Questions & Answers

Q (J. Va'vra): The Malter ignition depends on the density of transient ionization. For example, as shown by HERA-B, slow protons or ions may be good ignitors of the Malter effect. The fact thtat you did not observe the Malter effect may mean that you did not have good ignitors when using a Cs source. For example, a good ignitor could be an alpha source.

A (V.S.): During the test of the CMS endcap chamber last year (2000) at the GIF at CERN, layer 2 was suddenly affected (ed.?) after increasing the gas flow rate by 40 times from 3 l/hour (= 1 vol./day) to 120 l/hr at the end of the test after having collected 0.3 C/cm. The rise of the current was practically unlimited with rates of 50 muA/min. The whole layer showed ~200 muA (under irr.) for a count rate of 18-20 kHz/cm². This Malter current of ~200-300 muA from this layer could be obtained with two conditions: GIF intensity or very high gas flow. This type of Malter current was only suppressed by decreasing the HV down to 2.7 kV (normal op. HV is 3.7 kV). After this, the usual dark current of ~10 nA was restored at 3.7 kV in layer 2.