Help with grounding an SSTC & safely storing PCB while coil is operating

[fillertext]

First post and unsure if this should go here or under Solid State Tesla Coils so sorry if this is in the wrong place! This got quite long so I've numbered each question to hopefully make any responses easier to structure.

BRIEF (but necessary) CONTEXT
I'm a physics student about 3/4 of the way through building my first Tesla coil, following this tutorial (https://www.youtube.com/watch?v=zCf-PwXsG_E) by LabCoatz. It's an SSTC designed to be run on mains supply. The schematic (https://1drv.ms/i/c/b5cad68aa0baaa0a/EZxgM9jw7npHpOghGR4RXkQB2zDsglLLqo5fXYhwVEHixw?e=sebj3W) has the coil grounded through mains ground but I'm going to be powering this coil in my school and have been told I'm not to tamper with the mains directly in any way. Fair enough.
Sidenote: the circuit is grounded through a high-voltage benchtop power supply with a ground terminal that presumably goes through to the mains ground anyway but it's the secondary coil itself they're concerned about being connected to mains.

QUESTIONS
The first question then is: (1) how should I go about safely grounding my secondary? From what I've researched, I've gathered this can be done by jamming a copper rod into the Earth but this seems more suitable for higher voltage coils & also won't be possible for me, given I want the coil to operate indoors. Other suggestions include a sheet of aluminium and this is where I'd like some advice - (1a) how do I do that safely i.e. where should that sheet be kept in relation to the coil and circuit & how should it be stored? (1b) How large should this sheet be? (1c) Or are there any other safer options you would suggest (remembering this coil should be able to operate indoors)?

The second is: (2) how can I protect the PCB from interference while the coil is operating? The tutorial suggests keeping it inside a box layered with grounded aluminium. (2a) How should I ground that aluminium layer? I imagine it's silly to use the same ground as the secondary but obviously correct me if I'm wrong. (2b) And is it stupid for the aluminium-layered box to be cardboard, given the potentially high temperatures involved? (2c) Finally, how should I prevent the PCB components from touching that aluminium layer? On the absolute last of my budget & don't have any kind of rubber mesh to place over the aluminium - may deconstruct a Tupperware box and tape this to the aluminium with insulating tape but, again, I'm concerned about temperature.

Would appreciate any responses! Even those calling these questions stupid - I'm inexperienced & very concerned about staying safe here & may be asking silly questions because of it. Thanks!

POTENTIALLY USEFUL COIL SPECS
Primary coil: 116mm diameter, in progress- planned 4-5 turns of 14awg insulated wire
Secondary coil: 9mm diameter, 170mm tall, ~560 turns of 32awg enamelled copper wire

[alan sailer]

I'm not sure what your school considers "tampering". The ground wire on a wiring system is designed to be used as a safety measure. Operating a coil using household ground can allow nasties to get into the grounding system. Quality electronics is designed to deal with the crud that happens in a typical AC system.

I am sure that there are situations where tesla coils hooked up to a residential ground have caused issues. But I've built a dozen or so tesla coils from 40 watt to several kilowatts and have used a residential ground as my only ground. No dead computers, routers, power supplies, scopes etc.

Would a ground rod be better? Sure but I'm not sure how. Counterpoise? I'm sure it has benefits, but the coils that I have built and run put out nice sparks in proportion to their power consumption. No ground rods, no counterpoise.

And of course, others with more electronic experience may have different ideas. Asking these questions is a good idea since it's not your stuff that could be hurt, it's the schools stuff.

Cheers.

[davekni]

Sidenote: the circuit is grounded through a high-voltage benchtop power supply with a ground terminal that presumably goes through to the mains ground anyway but it's the secondary coil itself they're concerned about being connected to mains.

Are you sure they are concerned about mains ground connection and not just mains hot and neutral?  Most electronic equipment (scopes, signal generators, etc.) are connected to mains ground.  Circuits being tested are also connected to mains ground through the equipment ground, such as a scope probe connection.  Would you not be allowed to measure secondary current using a shunt resistor and scope?

Other suggestions include a sheet of aluminium and this is where I'd like some advice - (1a) how do I do that safely i.e. where should that sheet be kept in relation to the coil and circuit & how should it be stored? (1b) How large should this sheet be? (1c) Or are there any other safer options you would suggest (remembering this coil should be able to operate indoors)?

A counterpoise is great.  Aluminum sheet or screen or foil works well, but steel is fine too, such as chicken wire.  Easiest to place on surface such as table top, then set coil (including drive electronics) on top of counterpoise.  Electronics could be underneath, but that's inconvenient and not necessary.  Larger is always better.  Counterpoise radius on the order of height of entire coil (including base) should be plenty.  (Of course no need to be round.)
Still best to connect counterpoise to line ground besides to secondary bottom.  Likely OK without line ground connection, but I've never tried such.  Always had both a counterpoise and line ground for my coils.  Counterpoise will reduce current into line ground.

And is it stupid for the aluminium-layered box to be cardboard, given the potentially high temperatures involved?

My largest coil uses a foil-lined cardboard box.  Works just fine, even though not ideal aesthetically.  I have a scrap of polyethylene foam between box bottom and ECB, though my ECB does not run very hot.  Mylar should be good to any temperature your ECB will survive.  Or polypropylene or polyimide (Kapton) or polyamide (nylon) or many other options.

Hope your build goes well!