Let's take a look at varying frequency versus beam current for 16O2+. Starting RF values shown below. FC6 = 1.09enA.

What I did: Pan RF frequency between about 12.5GHz and 14GHz. Plasma seemed to extinguish at a frequency under 13GHz.

What I found: Two peaks on the low side, right around 13GHz.

How I proceeded: I panned across those two peaks for stability. I found that the stronger peak in fact was noisier, and also at risk of losing plasma.

Screengrabs:

1. Starting RF settings

2. Lower window of "good" RF frequency.

3. Higher window of "good" RF frequency.

4. Original beam plot.

5. Beam plot at middle of "good" frequency range.

6. Beam after frequency restored to starting value.

7. Frequency survey correlation plot.

As it turns out and as you can see, the original frequency not only provides the same intensity of beam, the beam is also visibly more stable. (Keerthi found this one.)

Lesson learned: Discovery of the ideal frequency is an iterative process. At least three passes, each successively finer, are required.

In anticipation of 16O2+ delivery mid-week, we checked 16O2+ production from the Supernanogan source. No problem. We did have to use the tightest slit settings to achieve a low enough current for the user. Here are emittance scans, normal and with our test booster amplifier inline respectively. Subsequently we set up the line to match into the RFQ. Bias is at 16.32KV. Then we returned the mass selection to 16O7+ for the night. A final emittance scan of 16O7+ for today is shown. It clearly needs a stronger signal. With some slight tweaks, there are some 1nA of 16O7+ on FC6 now.

Controls is rebooting IOSIOC. I have inserted MCIS:FC1 for the duration. Let's see what comes of it all.

Later... As expected, the reboot zeroed our optics. ICR issued a FR#4179 on it. Meanwhile, I rechecked the A/q calibration, and found it off a little. Below are before and after shots. The latter shows scanning in both directions. I didn't expect this large a hysteresis. On the other hand, the crossover points make nice reference points for known A/q values.

Later... Controls is investigating the FR! MCIS:FC0 in, and let them 'ave at 'er.

Here are some pics and data from total MCIS beam on FC3 overnight. A bit inconclusive, but there may be a temperature correlation.

Attached is the scheduled work for OLIS next week.

Microwave source is up and running.

Supernanogan: grounding rod is stuck, RF generator does not clear the interlocks (controls?)

LEBT: FC3 air leak, in is out, out is in

Supernanogan is ready with 22Ne+4 for upcoming CSB run. EL, HV and RF are on. The anlyzing magnet and the other optics are set for A/Q=5.5.

A 2nA of 22Ne+4 is sitting at the FC6. If require more current, increase the RF up to 25W or change the frequency to 13.256GHz.

33S development is completed.  A 3nA of 33S+5 can be produced with 10W of RF power and 2.5mm aperture.

If more beam is needed apertures and the power must be increased.  There are some consequences for doing this.

MCIS optics and RF are off for the night.

Klixon at the OLIS bemding magnet is not funtioning properly.

We will be delivering a 28keV beam to the tuning boys tomorrow for further diagnosis of the 8pi line. In anticipation, I restarted the MWS with 20Ne1+ beam. With slits out, there are around 2uA on FC6. Emittance scan of current tune below.

Same tune again with slits in a 1mm, emittance scan attached.

Gas flow presently at 0.5ccm. I will lower it slightly, as IOS pressure is a little high.

Save: 100113_1830.snapiosfc6

All turbos in the OLIS and MCIS are off. No controls for the MCIS. Pumps switched of by pulling the CG cable.

All the gate valves are off. All bypass are removed

Source stayed up quietly overnight. Current dropped off gradually. I will tweak things shortly.

Beam tweaked up to 3eµA. Pressure is ~5e-7 Torr. Plan for today will include a rework of the arc and plasma power supply wiring to achieve higher V on arc and opposite polarity on plasma.

Later... First iteration of plasma polarity swap was a bust. The supply couldn't handle the back EMF or something, and the beam was unstable. Keerthi tweaked something... Now it's stable. Some measurements taken with varying the arc supply and tweaking the rest to follow. More of the same to come. Meanwhle, there are 6.5eµA of 4He2+ on FC6 presently.

Today we swapped power supplies between the arc and plasma electrode. This gives us a higher voltage range on the arc, at the possible expense of current limiting. We plan an extended round of development in this mode.

Four larger apertures were installed yesterday. This morning we fired up the modified source. It lit immediately. Plenty of beam. Development at 28kV, then scaled to 15kV. Beam intensities and ratios did not scale. Thesis: Space charge effects are too much for 15kV. Also, I3 accel-decel lens p/s needs work. We added a ballast to it today; p/s in tomorrow, then retest.

Today we vary source gas pressure.

Later... Several iterations of pressure, tuning and standing on our heads. Representative emittance scans attached below. TBC tomorrow.

Yesterday: Busy! Source filment changed last night. Source pumped overnight. First start this morning.

Today: Busy! Nutshell: A/q=2 passed to Marco for isotope verification at MEBT.

Later ~16:00 Beam on MEBT:FC5, an historic first for achieving A/q = 2 through RFQ. 1.6enA of (likely) 4He2+. Tuning to FC7 continues.

Later ~16:50: Blips on FC7. Real? Stay tuned.

First emittance scan at 4kV taken and attached. It's rough but indicative.

The OLIS cage was open over the weekend. IOS pressure is in the 4e-7 range, with source gas manifold closed and external helium bottle slightly opened through the metering valve. Today's game plan is being discussed presently.

Later ~11:00: Restart source. 50enA of A/q=2 at FC6. We had planned to restart with background source gas, but pressure is too low in gas lines, and a plasma is forming there. I have opened helium on gas manifold, with flow controller at zero SP. ~0.5ccm result. Background pressure ~4e-7 Torr; present pressure = ~1e-6 Torr.

Later ~15:00: Tweak source and IOS. Presently we have 0.5uA of A/q=2 on FC6. Big contributors: EE + vertical steering. Attached pic shows beam since ~startup this morning and a flurry of activity around midday. I will begin some source gas tests shortly.

Later... Source gas tests part one completed. Solenoid valve upstream of flow controller closed, then flow readback, pressure drop and FC^ noted until source gas line became a "neon" lamp. Part two barely begun, when FUG blew a fuse on normal startup and (how embarrassing) we don't have replacements handy. Also, upon opening the RG helium line, we found it was tricky to get a good pressure. We have it now. Fuse will have to wait until man~ana, though.

Fuse for FUG power supply obtained and installed. Source is up and warming up. ~100enA on FC6.

Later ~14:00: Tweak things up. We now have a more stable 380enA on FC6. IOS:IG1 = 7e-7 Torr.

Later ~15:15: Adjust source gas metering valve "just a little"... and effectively vent the tank. This needs work. Recover, restart source. Wait and watch how beam responds to gas pressure. See attached stripchart.

Later ~16:00: Increase arc power & filament current. Arc current jumps from <100mA to >3A. Also increased current load on bias & EE.

Arc = 135V @ 3.0A

Fil = 3.25V @ 138A

Bias = 28kV @ 788uA.

EE = 2.07kV @ 4.9mA

PE = 97V @ 149mA

Gas = 0.41ccm

First mass scan attached with arc current at 3A.

Second mass scan in progress

CUSP source was off for the night, following Keerthi's development. He had increased the current on FC6 and the arc current substantially. More later.

Meanwhile, restart source and let it condition for a bit.

Later ~14:00 we have 200enA on FC6. Source gas is shut off presently. Time for some mass scans. Strategy: Identical mass scans without and with source gas, to check background ratios.

Later ~15:00: Mass scans with source gas closed complete. Note: IOS pressure is 5.25e-7 Torr, slightly higher than earlier. It was ~3e-7 this morning. Possible leak in gas manifold fitting?

Later ~16:30: Try out different combinations of gas and source parameters. We cannot get the gas flow low enough so far. Optimal source:

Fil = 130A (3.1V)

Arc = 67V (0.9A)

FC6 = 7.5eµA 4He2+ & H2

Note: Increasing any of these parameters much above these numbers causes the bias to current-limit at 1mA.

Later ~18:00: Check beam current at H+ and H3+:

FC3 = 140µA

FC6 = 1.42A at A/q = 1 i.e. H+

FC6 = 149enA at A/q = 3 i.e. H3+

FC6 = ~80µA at A/q = 4 i.e. 4He1+

FC6 = 1.78eµA at A/q = 16 i.e. O+

FC6 = 2.29A at A/q = 18 i.e. H2O

Plot 1: FC6 current for last evening.

Plot 2: Scan 0 to 5 and back.

Plot 3: Scan 0 to 40 (same parameters as yesterday).

Plot 4: Scan 0 to 40 and back.

Plot 5: Combo development session stripchart.