Double-walled quartz immersion well for use with 7863, 7864, 7865, 7891, or 7885 pilot scale reactors and 7825 lamps only. Coolant is introduced through a 4.8 mm I.D. PTFE tube attached to a glass tube and secured with a #7 Ace-Thred bushing. PTFE tube extends down the annular space to insure flow of coolant from bottom of well upward to outlet. Well is used with 7506-14 nylon bushing with FETFE O-Ring to form a compression type seal with threaded reaction vessels. Well offers a greaseless connection and can be adjusted to desired height. The Ace-Thred means easier dismantling since it prevents any chance of freezing.