GEOGRAPHIC AND SEGMENT INFORMATION - REPORTABLE SEGMENT (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Sales	$ 4,296	$ 6,649	$ 9,293	$ 12,278
Income (loss) from operations	(6,167)	(4,422)	(13,659)	(10,152)
Interest income	7	403	223	826
Interest expense	(8)	0	(14)	0
Other income (losses), net	(14)	(200)	412	(495)
Income tax (benefit) expense	(1,492)	76	(6,397)	82
Operating Segments | Advanced Energy
Segment Reporting Information [Line Items]
Sales	2,867	5,350	6,853	9,721
Income (loss) from operations	(3,292)	(968)	(7,276)	(4,296)
Interest income	0	0	0	0
Interest expense	0		0
Other income (losses), net	0	0	0	0
Income tax (benefit) expense	0	0	0	0
Operating Segments | OEM
Segment Reporting Information [Line Items]
Sales	1,429	1,299	2,440	2,557
Income (loss) from operations	584	136	831	727
Interest income	0	0	0	0
Interest expense	0		0
Other income (losses), net	0	0	0	0
Income tax (benefit) expense	0	0	0	0
Corporate & Other
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Income (loss) from operations	(3,459)	(3,590)	(7,214)	(6,583)
Interest income	7	403	223	826
Interest expense	(8)		(14)
Other income (losses), net	(14)	(200)	412	(495)
Income tax (benefit) expense	$ (1,492)	$ 76	$ (6,397)	$ 82