A "stack of AA batteries" as described would be a measure of electrical potential (i.e. voltage), not electric field strength (Volts / unit-length in the applicable dimension(s)).
It's been known for quite some time that high density static electric field "break-downs" generate electromagnetic radiation all throughout the spectrum--look at any wide-band antenna's reception next to any spark-gap generator. It doesn't take much--even the piezoelectric igniter on a grill wand will do it.
One can also generate X-rays by rapidly unrolling Scotch tape. It the same phenomena on a _much_ smaller scale. What's "new" here are the two distinct types of gamma discharges indicating (likely) very different field breakdowns--not that these gamma rays themselves are being produced.
A "stack of AA batteries" as described would be a measure of electrical potential (i.e. voltage), not electric field strength (Volts / unit-length in the applicable dimension(s)).
It's been known for quite some time that high density static electric field "break-downs" generate electromagnetic radiation all throughout the spectrum--look at any wide-band antenna's reception next to any spark-gap generator. It doesn't take much--even the piezoelectric igniter on a grill wand will do it.
One can also generate X-rays by rapidly unrolling Scotch tape. It the same phenomena on a _much_ smaller scale. What's "new" here are the two distinct types of gamma discharges indicating (likely) very different field breakdowns--not that these gamma rays themselves are being produced.