Physics 405, Spring 2001
Last updated 03/13/01
Helpful Hints, corrections, etc.
Here is a link to the NIST Reference
on Constants, Units and Uncertainty .
You may find this useful in analyzing your data. This is the last word on how to
properly quote uncertainties in your measurements.
Experiment I: Measurement of the Speed of
Light
Experiment II: Experimental Atomic Spectroscopy
- Optimizing the slit widths for the best resolution is best done with the H/D source.
- Turn the flourescent lights off when you are making a scan to cut down on the electrical
noise coming from the lights.
- Don't forget to calibrate the display on the microprocessor against the dial indicator
on the monochrometer. If you don't, you may run the monochrometer into either its upper or
lower limit. If this happens, contact one of the instructors right away so it can be
reset.
Experiment III: The Franck-Hertz Experiment
- Give yourself a quick refresher on RC circuits for oscillating signals before connecting
the electronics.
- REMOVE THE RC FILTER WHEN YOU CALIBRATE THE 40V POWER SUPPLY!
- Allen suggests turning off the temperature controller just before taking a scan with
ACQUIRE (don't forget to turn it back on though.).
- Although it should be possible to simultaneously record the Franck-Hertz tube current in
channel 0 and the ramping voltage in channel 1, it is difficult. Only Dr. Webb has
succeeded in doing this!
Experiment IV: Determining Planck's Constant
Experiment V: There Ain't None!
Experiment VI: Measurement of (e/m) for the
electron
- You MUST go over the operation of the vacuum system with either Allen Monroe, Tom
Baldwin, or one of the instructors before starting the experiment! See also Appendix A in
the lab manual.
- Here's a Helmholtz coil calibration curve.
Here's a more
recent calibration from 1996, plus a plot showing the residual
errors.
- Think about the contribution of the earth's field to your measurement, and how you can
account for (or get rid of) it.
- See the updated instructions for operating the vacuum
system, replaces Section III of Appendix A.
Experiment VII: Introduction to Nuclear Spectroscopy I
- NOTE: this experiment along with VIII and IX use a data acquisition and software
package specifically designed for nuclear spectroscopy. You should take a little
time to familiarize yourself with the program before attempting to take data. See Appendix C
for a brief description of the program.
- For this experiment, and also exps VIII and IX, here is a brief description on using
either the Tektronix
2245A or the digital Tektronix
TDS360 scopes.
Experiment VIII: Introduction to Nuclear Spectroscopy II
- See the notes in exp VII regarding data acquisition.
- You can find more and up-to-date information about the particular nuclei you are
studying at the National Nuclear Data Center at
Brookhaven National Lab. This picture of the 56Mn->56Fe
gamma ray scheme was generated using the MIRD database. Also, take a look at the 228Th
spectrum hanging on the wall near the Exp 8 setup for your energy calibration.
- For this experiment, and also exps VII and IX, here is a brief description on using
either the Tektronix
2245A or the digital Tektronix
TDS360 scopes.
Experiment IX: Gamma-Gamma Angular Correlation
- See the notes in exp VII regarding data acquisition.
- Use the fast oscilloscope (Tektronix
2245A or Tektronix
TDS360) from exps VII/VIII or exp XI to check the coincidence timing! Follow the
signals all the way through the circuit to make sure the signals going into the
coincidence circuit are properly timed.
- There is a stronger 60Co source inside the little lead can in the lead-lined
box. The metal rod (not the block) is the active area of the source. Calculate for
yourself how much stronger this source is than the one in the wooden box.
- The detection efficiency of the two-detector system changes as a function of angle. This
affects the overall shape of the data. The effect can be estimated using Monte Carlo
techniques. Run the Monte Carlo Program called MC.EXE(written
by Prof. CC Chang) to see the effect. It is located in the DOS directory of programs
on the lab computers.
- You will need to fit your data to either Legendre Polynomials, or to equation IX-1 in
the lab manual. A sample fitting program, using EXCEL, can be found at p:\p405\Analysis Tools\Excel Tools\ParaFit-mc.xls. This is a
parabolic fit with 3 parameters. The data have been entered such that the independent
variable is cos^2(theta). It's rather clumsy, but functional.
Experiment X: The Hall Effect in Metals
- You MUST go over the vacuum system with either Allen Monroe, Tom Baldwin, or one of the
instructors before starting the experiment! See also Appendix A.
- You will need to take a look at Appendix E
on sample preparation, which is not in the lab manual.
- See one of the instructors regarding thickness measurements: there is a relatively new
apparatus donated by Dr. Webb. A manual for it can be found in this Appendix D.
Experiment XI: Cosmic Rays
- To get the solid angle of the detector system, you have to do a four-dimensional
integral: you can either use Mathematica, or you can look for the nifty little pascal
program written by Prof. C.C. Chang, called INTEGRAL.EXE,
which is located on the P405 PCs in p:\p405\exp11\ .
- Figure XI-2 in the lab manual is OK, but not quite accurate. This one
is a little better.
- Use the digital oscilloscope (Tektronix
TDS360) to check the coincidence timing.
- BE SURE THE HV SUPPLY is set to NEGATIVE (-)!
- Further information on the various components of cosmic rays can be found in the
Particle Data Group's Review of
Particle Properties. Look under Astrophysics and Cosmology, then under Cosmic
Rays.