Difference between revisions of "Bubble Chamber Beam Test September 2015"
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| Line 41: | Line 41: | ||
* ''Suppression of <sup>14</sup>N(γ,p)<sup>13</sup>C events:'' | * ''Suppression of <sup>14</sup>N(γ,p)<sup>13</sup>C events:'' | ||
| − | # Start with beam at K.E. | + | # Start with beam at K.E. 7.0 MeV |
| − | # Increase beam K.E. by 0.2 MeV steps all the way to 8. | + | # Increase beam K.E. by 0.2 MeV steps all the way to 8.6 MeV |
# Adjust beam current to maintain a bubble rate of few per minute | # Adjust beam current to maintain a bubble rate of few per minute | ||
# Reproduce the overall rate shown above | # Reproduce the overall rate shown above | ||
Revision as of 16:46, 6 September 2015
Bubble Chamber Beam Test
- Chamber is filled with natural N2O
- Cross sections:
The cross sections are shown in the following figure:
- Expected rates:
The expected rates are calculated with 3 cm cell thickness and thin radiator.
- The expected rates are shown in the following figure:
- The expected rates from oxygen isotopes are shown in the following figure:
- Run Plan:
- Check if Bubble Chamber is working properly:
- Start with K.E. of 7.7 MeV
- Determine an initial pressure and temperature with no beam
- Measure bubble rate. The expected rate is 1 bubble per sec at 10 µA
- Measure rate vs beam current (0.01 – 10 µA)
- Suppression of 14N(γ,p)13C events:
- Start with beam at K.E. 7.0 MeV
- Increase beam K.E. by 0.2 MeV steps all the way to 8.6 MeV
- Adjust beam current to maintain a bubble rate of few per minute
- Reproduce the overall rate shown above
- At K.E. of 8.5 MeV, increase the chamber threshold by increasing the pressure. Suppress the 14N(γ,p)13C events.
- Once 14N(γ,p)13C is suppressed, the rate should drop by three orders of magnitude
- Measuring rates from 18O(γ,α)14C:
- Now the chamber is at the new pressure
- Start with beam at K.E. 7.2 MeV
- Increase beam K.E. by 0.2 MeV steps all the way to 9.2 MeV
- Adjust beam current to maintain a bubble rate of few per minute
- Reproduce the overall rate from oxygen isotopes shown above
- Note the change in slope of rates vs. beam K.E. and the sharp kink around 7.6 MeV
- Measuring 18O(γ,α)14C cross section:
- Start with beam at K.E. 7.4 MeV
- Increase beam K.E. by 0.1 MeV steps all the way to 8.4 MeV
- Adjust beam current to maintain a bubble rate of few per minute
- Perform Penfold-Leiss unfolding
| Beam Kinetic Energy (MeV) | Beam Current (µA) | Time (hour) |
| 7.4 | 10 | 10 |
| 7.5 | 10 | 10 |
| 7.6 | 10 | 5 |
| 7.7 | 2 | 5 |
| 7.8 | 2 | 5 |
| 7.9 | 1 | 5 |
| 8.0 | 1 | 5 |
| 8.1 | 0.8 | 5 |
| 8.2 | 0.4 | 5 |
| 8.3 | 0.2 | 5 |
| 8.4 | 0.2 | 5 |
The expected yield is shown in the following figure:
The Penfold-Leiss unfolded cross section is shown in the following figure:
