1. Electron interactions with CO 2 Bob Merlino Department of Physics and Astronomy The University of Iowa Iowa City, IA U. S. Department of Energy National Energy Technology Laboratory May 30, 2008

2. Electron impact ionization

3. Electron attachment to CO 2 Y. Itikawa, J. Phys. Chem. Ref. Data, 31,749, 2002 CO 2 cannot permanently bind an electron, so that is metastable, with lifetimes in the microsec to millisec range, decaying back to CO 2 by auto- detachment: the electron attachment probability is enhanced if CO 2 is in an excited vibrational state electron energy (eV) attach. cross section (10 -18 cm 2 )

4. Devices at the University of Iowa Plasma Laboratory 2 Q machines with magnetic fields up to 0.5 T – 6 cm diam. by 2 m length, variable B profile – 6 cm diam. by 1 m length, which can also operate in the presence of micron sized dust particles A glow discharge, dusty plasma / multidipole device, 60 cm diam. x 90 cm length A multidipole/inductively coupled plasma device, 84 cm diam. x 130 cm length (The UI physics dept. has agreed to provide this device.)

5. Q machine / Discharge plasma This device can be operated either with a thermal, surface ionization plasma source (QM) which produces either as K or Cs plasma, or as a discharge device using He, Ar, Ne, Xe, N 2, by removing the hot plate and biasing the filament negatively. In the Q mode the electrons are relatively cold with Te ~ 0.2 eV In the discharge mode there are thermal electrons with Te ~ 2 – 5 eV and with a population of energetic electrons with Ee ~ 30 –100 V. B Hot Plate Langmuir Probe Hvac Pump Plasma hot filament K oven Cold Plate Solenoid coils Gas inlet

6. IOWA Q-3IOWA Q-2

7. Hot filament multidipole plasma source GAS TURBOMOLECULAR PUMP FILAMENT MAGNETS LANGMUIR PROBE T e  2 – 5 eV 84 cm 130 cm

8. Inductively coupled plasma source TURBOMOLECULAR PUMP GAS LANGMUIR PROBE T e  2 – 5 eV 84 cm 130 cm

9. Formation of The presence of is confirmed by observing the spectrum of ion cyclotron waves in the plasma is a metastable negative ion B = 0.3 T P(CO 2 ) = 6  10 – 5 Torr V probe = 15 V 10 dB K+K+ 0 100 200 300 400 500 Frequency (kHz)

10. Mass spectrometer measurements -160 -120 -80 -40 0 40 80 120 160 K + Cs + SF - 6 VOLTS 2 ion plasma K + / Cs + K + / SF 6 – plasma