Sending Digital Data TX-RX in a noisy environment

Hi. Forum!
It's me Peter and I need your help!
For my Master Thesis's Measurements I need to send analog acquired signals (4 currents of 10-20mA each) in a noisy environment (an ElectronBeamAccelerator that stays inside a bunker) 40meters away outside the bunker to my Instruments.
I have the Idea to use a commercial ADC that is controlled via classical RS232 to a PC that reads the currents and convert them digitally.
Now the problem is where to place the ADC block.Near the computer far away from the Accelerator or near the current sensor?? If near the sensor so the RS232 cable should be 40mt. long!! and catch all groundloops and noisy interferences.
My idea would be to convert RS232 to RS 445 transmit them 40mt. and then reconvert them to 232 locally near the pc. Have you any ideas or hints howto solve the problem else?
Any help will be very appreciated.
Regards
Peter

My opinion is to let the 4-20mA as is, convert them at the PC side with your ADC/RS232 and add a 232/232 galvanic isolation to avoid ground loops with your equipment. Is easier to spot and filter the interference on your analog lines then RS485.
You may consider also fiber optic transmission if the interference are considerable.

Thanks a lot for your reply.
So thinking to send them optically is not a good effort since the accelerator produces a lot of x-rays.
After severe calculus the current should go down to 20uA (heeeelp!)
And the ADC is now connected to USB to the PC port.
Sorry for the varying values but they are not all clear,due to intellectual property.

So as far as I understood, you would cover the distance analogically, bring this low currents along the 40mt. path? and then convert them near the PC right?

Thanks alot