This morning 2x RAL108 +/-15V PSUs were borrowed from the Edinburgh equipment in the ISOLDE hall to check whether the same transient noise is observed at the +/-15V PSU 
outputs - this was confirmed. See https://elog.ph.ed.ac.uk/nToF/63

Following this test the same 2x RAL108 +/-15V PSUs were tested in the ISOLDE hall ( 19" rack adjacent to the HIE-ISOLDE GP scattering chamber ). 


PSU #1 Coutant HSC15-3.0

Setup and PSU details - attachments 1-4

DSO ch#1 +15V AC/1M, ch#2 -15V AC/1M - y: 5mV/div x: 400ns, 4us & 40us/div - attachments 5-7


PSU #2 Farnell MX2

Setup and PSU details - attachments 8-10

DSO ch#1 +15V AC/1M, ch#2 -15V AC/1M - y: 5mV/div x: 400ns, 4us & 40us/div - attachments 11-13


Conclusion 

The noise of the 2x RAL108 +/-15V PSUs differed somewhat ( frequency and structure of HF transients ) from each other in the ISOLDE test.

Compared to the EAR2, n_TOF test the amplitudes were c. 10x smaller and the HF transient frequency and structure differed.

This appears to confirm that the primary problem is the ac mains power in EAR2, n_TOF - input and/or output filtering is required.