GEOGRAPHIC AND SEGMENT INFORMATION - Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Sales	$ 9,114	$ 11,831	$ 31,899	$ 31,693
Income (loss) from operations	(5,782)	(3,968)	(17,629)	(12,756)
Interest income	73	2	93	9
Interest expense	(1)	(3)	(12)	(9)
Other income (loss), net	(35)	(192)	551	(188)
Income tax expense	50	73	216	246
Operating Segments | Advanced Energy
Segment Reporting Information [Line Items]
Sales	7,080	10,313	26,258	27,951
Income (loss) from operations	(1,174)	52	(3,765)	(224)
Interest income	0	0	0	0
Interest expense	0	0	0	0
Other income (loss), net	0	0	0	0
Income tax expense	0	0	0	0
Operating Segments | OEM
Segment Reporting Information [Line Items]
Sales	2,034	1,518	5,641	3,742
Income (loss) from operations	356	328	1,142	588
Interest income	0	0	0	0
Interest expense	0	0	0	0
Other income (loss), net	0	0	0	0
Income tax expense	0	0	0	0
Corporate & Other
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Income (loss) from operations	(4,964)	(4,348)	(15,006)	(13,120)
Interest income	73	2	93	9
Interest expense	(1)	(3)	(12)	(9)
Other income (loss), net	(35)	(192)	551	(188)
Income tax expense	$ 50	$ 73	$ 216	$ 246