Differentiating between gas discharge and cathode ray I am trying to build a cathode ray tube but my vacuum pump is a fridge compressor which sucks at achieving a good vacuum! However I am getting a cathode ray like glow inside the vacuum chamber.
Now to determine weather its just gas discharge or actual cathode ray I brought a magnet near it and observed no deflection of the beam, thereby concluding that its just gas discharge. But the doubt is that the magnet is not that powerful and also the beam is 1-2 cm far from the walls of the vacuum chamber( the closest that I can bring the magnet.
My question is that weather my conclusion is correct that its just gas discharge and what other ways do I have to test weather its gas discharge glow or cathode ray.
 A: With permanent magnets, there's no easy way to tell what the magnetic field strength is at a given point without some more serious equipment. Following the '19th century gentleman inventor' vibe of your question, I recommend you obtain/construct a set of Helmholtz coils and run a known current through them. Near the center of the construction, these coils produce a nearly uniform magnetic field of strength
$$ B = \left(\frac{4}{5}\right)^{3/2} \frac{\mu_0 N I}{R} $$
where $I$ is the current, $N$ is the number of turns on each coil and $R$ is their radius.
If the tube voltage is $V_\mathrm{tube}$, you have everything you need to calculate the the perpendicular acceleration due to Lorentz force, $a_\perp = \frac{e}{m_e} v \times B$, where you can guesstimate $$v_\mathrm{elec} \approx \sqrt{\frac{2 e V_\mathrm{tube} d}{m_e L}}$$
where $d$ is the distance from the cathode to the center of the coils,  $L$ is the distance from anode to cathode, and $e>0$ is elementary charge.
If you know the rough orders of magnitude of all of these, you should know for certain whether $a_\perp$ is measurable or not.
An added benefit to making these coils is being able to electrically control the cathode ray, if that is indeed what you have.
