Our first tests with blast field on show that we lose ca. 60-70% of the
flow. This is before we use the MFT.
We can still find a transition but now from that value we infer 60 %
dissociation. Of course the MFT transition may not be 100 % efficient now.
A lower dissociation is consistent with a flow reduction. A lower
efficiency in the MFT 2-3 should populate less the 3 state, so the flow
reduction could be less and may lead us to a wrong estimate of the
dissociation. Of course, as vitaly suggests, we could have field dependent
alignement problems
Bottom line: increased flow by about a factor of 10 since last week. No
"direct" measurament of dissociation. Tuned MFT and estimated atomic
flow from that. Problems with blast field on.
Will take data w/ just the ABS flow, with no additional reduction from MFT
opeing to find a calibration of the number of protons/cm2 and since the
MFT is off we can take additional flase asymmetry data.
-- ________________________________________________________________________________ Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124 research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^On Sat, 14 Dec 2002, Tancredi Botto wrote:
> > All day devoted to ABS. ABS dissociator was re-installed at around 2 pm. > Flow measuraments give ligit pressures as follows (sxpoles in) > > status ligit (torr) > > No abs flow 0.8e-9 > > injection valve open > Dissoc. RF off 5.5E-8 > > Dissoc RF ON 1.2E-7 > > > RF_on-RF_off gives an idea of flow of atoms, after rejection of the > 3,4 states *and* amplification from sx poles units. The above pressure > differentials were constant for a number of values of diss. RF power > and H2 flow, consistently with what was measured with a QMA 1 month > ago and in general with saturated dissociator operation. > > Note, we have not optimized the nozzle position with respect to the > skimmer. We now have the capability to do so without opening vacuum. > The nozzle alignement was visually inspected, nevertherless. > > We observed Delta-P = 6.7E-8 torr. If this was all atoms, it corresponds > to 1.5E16 At/s. However we know only a fraction is atoms. > If an 80 % fraction is atoms, the atomis flow is 1.2 E16 At/s > > We proceeded to try measure dissoc fraction with the QMA (sxpoles off). > We have chopper signal but no chopped signal. We have no M=2 > signal. We discard "dissociation fraction" masuraments for now. > > > We turned on the MFT units. With blast off, having the MFT on (at 60 MHz, > 4.5 A current to the static field) reduces the differential flow by 40%. > In other words, the dissocation fraction -as measured from the MFT - > seems to be 80-85%. This is an upper limit as we assume that the MFT > efficiency is 100% Note, at the same time, with the qma signal alone, > we roughly estimate a diss. fraction of 2/3, with larger uncertainties. > > With these caveats, then our estimate of a 1.2E16 At/s flow becomes > more realistic. > > > We will leave ABS on, MFT on for tonight and measure one full shift. > The holding field will be at 45 deg. > > > Abs work will continue tomorrow, when we will optimize intensity > at the nozzle/skimmer interaction. We realize that this is not an > optimization of actual flow inside the storage cell (rather of the flow to > the scatt chamber). The QMA needs to be looked at at somepoint. > > > -- VZ, TB, NM > > ________________________________________________________________________________ > Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124 > research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949 > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >
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