Patent Publication Number: US-2021170116-A1

Title: Heating smokeable material

Description:
PRIORITY CLAIM 
     This application is a continuation application of U.S. patent application Ser. No. 14/779,210, filed Sep. 22 2015, which is the National Stage of International Application No. PCT/EP2014/055485, filed Mar. 19, 2014, which in turn claims priority to and benefit of United Kingdom Patent Application No. GB1305294.9, filed Mar. 22, 2013. The entire contents of the aforementioned applications are herein expressly incorporated by reference. 
    
    
     FIELD 
     The invention relates to heating smokeable material. 
     BACKGROUND 
     Smoking articles such as cigarettes and cigars burn tobacco during use to create tobacco smoke. Attempts have been made to provide alternatives to these smoking articles by creating products which release compounds without creating tobacco smoke. Examples of such products are so-called heat-not-burn products which release compounds by heating, but not burning, tobacco. 
     SUMMARY 
     According to the invention, there is provided a smokeable material heating apparatus comprising a substrate and at least one printed heating element arranged to heat the substrate to a smokeable material volatilizing temperature and thereby cause the substrate to volatilize at least one component of smokeable material for inhalation. 
     The heating element may be located at least partially inside the substrate. 
     The coefficient of thermal expansion of the heating element may be substantially equal to the coefficient of thermal expansion of the substrate. 
     The heating element may be chemically bonded to the substrate. 
     The heating element and the substrate may comprise a single sintered structure. 
     The heating element may comprise an electrically resistive trace in the substrate. 
     The substrate may comprise a ceramics material. 
     The substrate may be proximal a smokeable material heating chamber configured to contain the body of smokeable material during heating. 
     The apparatus may comprise a plurality of the heating elements arranged in layers inside the substrate. 
     The layers of heating elements may be interconnected by heating element vias through the substrate. 
     According to the invention, there is also provided an apparatus comprising a heater configured to heat smokeable material to volatilize at least one component of the smokeable material for inhalation, wherein the heater comprises a substrate and a heating element with substantially equal coefficients of thermal expansion. 
     The heating element may be printed to the substrate. 
     The heating element may be arranged to heat the substrate to a temperature sufficient for the substrate to volatilize at least one component of smokeable material located in an adjacent smokeable material heating chamber. 
     The heating element may be located at least partially inside the substrate. 
     The heating element may be chemically bonded to the substrate. 
     The heater may comprise a sintered structure comprising the heating element and the substrate. 
     The heating element may comprise an electrically resistive trace in the substrate and/or the substrate may comprise a ceramics material. 
     The apparatus may comprise a plurality of the heating elements arranged in layers inside the substrate. 
     The layers of heating elements may be interconnected by heating element vias through the substrate. 
     According to the invention, there is also provided an apparatus comprising a heater configured to heat smokeable material to volatilize at least one component of the smokeable material for inhalation, wherein the heater comprises a multiply layered structure of ceramic material and electrically resistive heating elements. 
     The heating elements may comprise electrically resistive traces in the ceramic material. 
     The heating elements may be chemically bonded to the ceramic material in a sintered structure. 
     The coefficient of thermal expansion of the ceramic material may be substantially equal to the coefficient of thermal expansion of the heating elements. 
     The heating elements may comprise Tungsten and the ceramic material may comprise Aluminum Nitride Ceramic. 
     The heating elements may be printed to the substrate. 
     The heating elements may be arranged to heat the ceramic material to a temperature sufficient to volatilize at least one component of smokeable material located in a heating chamber adjacent the ceramic material. 
     The heating elements may be located inside the ceramic material. 
     Layers of the heating elements may be interconnected by heating element vias through the ceramic material. 
     According to the invention, there is also provided an apparatus comprising a heater arranged to heat smokeable material, wherein the heater comprises a substrate and at least one heating element located inside the substrate so as to heat the substrate to cause the substrate to volatilize at least one component of the smokeable material for inhalation. 
     The heater may comprise a thermal expansion-matching structure. 
     The coefficient of thermal expansion of the heating element may be substantially equal to the coefficient of thermal expansion of the substrate. 
     The heating element and the substrate may be sintered to form a chemically bonded structure. 
     The substrate may comprise a ceramics material and the heating element may comprise an electrically resistive trace material. 
     The substrate may be proximal a smokeable material heating chamber configured to contain the body of smokeable material during heating. 
     The apparatus may comprise a plurality of the heating elements arranged in layers inside the substrate. 
     The layers of heating elements may be interconnected by heating element vias through the substrate. 
     The apparatus may be configured to heat the smokeable material to a smokeable material volatilizing temperature of at least 120 degrees Celsius. 
     The apparatus may be configured to heat the smokeable material to a smokeable material volatilizing temperature of between 120 degrees Celsius and 250 degrees Celsius. 
     The apparatus may be configured to heat the smokeable material to a smokeable material volatilizing temperature of between 130 degrees Celsius and 180 degrees Celsius. 
     The invention may facilitate use of at least one printed heating element to heat a substrate to a smokeable material volatilizing temperature and thereby cause the substrate to volatilize at least one component of smokeable material for inhalation. 
     The invention may facilitate use of a heater comprising a substrate and a heating element with substantially equal coefficients of thermal expansion to heat smokeable material to volatilize at least one component of the smokeable material for inhalation. 
     The invention may facilitate use of a heater comprising a multiply layered structure of ceramic material and electrically resistive heating elements to heat smokeable material to volatilize at least one component of the smokeable material for inhalation. 
     The invention may facilitate use of a heater comprising a substrate and at least one heating element located inside the substrate to heat the substrate and cause the substrate to volatilize at least one component of smokeable material for inhalation. 
     According to the invention, there is provided a method of heating smokeable material, comprising heating a substrate to a smokeable material volatilizing temperature using at least one printed heating element arranged to heat the substrate and causing the heated substrate to volatilize at least one component of smokeable material for inhalation. 
     According to the invention, there is provided a method of heating smokeable material, comprising heating a substrate to a smokeable material volatilizing temperature using at least one heating element located inside the substrate and causing the heated substrate to volatilize at least one component of smokeable material for inhalation. 
     For exemplary purposes only, embodiments of the invention are described below with reference to the accompanying figures in which: 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic illustration of layers of a smokeable material heater comprising a substrate and heating elements interconnected by vias between the layers; 
         FIG. 2  is a schematic, cross sectional illustration of an apparatus configured to heat smokeable material to release aromatic compounds and/or nicotine from the smokeable material; 
         FIG. 3  is a perspective, partially cut-away illustration of an apparatus configured to heat smokeable material to release aromatic compounds and/or nicotine from the smokeable material; 
         FIG. 4  is a perspective, partially cut-away illustration of an apparatus configured to heat smokeable material, in which the smokeable material is provided around an elongate heater divided into radial heating sections; 
         FIG. 5  is an exploded, partially cut-away view of an apparatus configured to heat smokeable material, in which the smokeable material is provided around an elongate heater divided into radial heating sections; 
         FIG. 6  is a flow diagram showing a method of activating heating regions and opening and closing heating chamber valves during puffing; 
         FIG. 7  is a schematic illustration of a gaseous flow through an apparatus configured to heat smokeable material; 
         FIG. 8  is a graphical illustration of a heating pattern which can be used to heat smokeable material using a heater; 
         FIG. 9  is a schematic illustration of a smokeable material compressor configured to compress smokeable material during heating; 
         FIG. 10  is a schematic illustration of a smokeable material expander configured to expand smokeable material during puffing; 
         FIG. 11  is a flow diagram showing a method of compressing smokeable material during heating and expanding the smokeable material for puffing; 
         FIG. 12  is a schematic, cross-sectional illustration of a section of vacuum insulation configured to insulate heated smokeable material from heat loss; 
         FIG. 13  is another schematic, cross-sectional illustration of a section of vacuum insulation configured to insulate heated smokeable material from heat loss; 
         FIG. 14  is a schematic, cross-sectional illustration of a heat resistive thermal bridge which follows an indirect path from a higher temperature insulation wall to a lower temperature insulation wall; 
         FIG. 15  is a schematic, cross-sectional illustration of a heat shield and a heat-transparent window which are moveable relative to a body of smokeable material to selectively allow thermal energy to be transmitted to different sections of the smokeable material through the window; 
         FIG. 16  is schematic, cross sectional illustration of part of an apparatus configured to heat smokeable material, in which a heating chamber is hermetically sealable by check valves; and 
         FIG. 17  is a schematic, cross sectional illustration of a partial section of deep-vacuum insulation configured to thermally insulate an apparatus configured to heat smokeable material. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the term ‘smokeable material’ includes any material that provides volatilized components upon heating and includes any tobacco-containing material and may, for example, include one or more of tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco or tobacco substitutes. 
     An apparatus  1  for heating smokeable material comprises an energy source  2 , a heater  3  and a heating chamber  4 . The energy source  2  may comprise a battery such as a Li-ion battery, Ni battery, Alkaline battery and/or the like, and is electrically coupled to the heater  3  to supply electrical energy to the heater  3  when required. It will be appreciated that, additionally or alternatively to the battery, the energy source  2  could comprise other types of source  2  such as one or more fuel cells and/or another non-battery sources of electricity. The heating chamber  4  is configured to receive smokeable material  5  so that the smokeable material  5  can be heated in the heating chamber  4 . For example, the heating chamber  4  may be located adjacent to the heater  3  so that thermal energy from the heater  3  heats the smokeable material  5  therein. Heat from the heater  3  heats the smokeable material  5  to volatilize aromatic compounds and nicotine in the smokeable material  5  without burning the smokeable material  5 . The smokeable material  5  may comprise a tobacco blend. A mouthpiece  6  is provided through which a user of the apparatus  1  can inhale the volatilized compounds during use of the apparatus  1 . 
     A housing  7  may contain components of the apparatus  1  such as the energy source  2  and heater  3 . As shown schematically in  FIG. 2 , the housing  7  may comprise an approximately cylindrical tube with the energy source  2  located towards its first end  8  and the heater  3  and heating chamber  4  located towards its opposite, second end  9 . The energy source  2  and heater  3  may extend along the longitudinal axis of the housing  7 . For example, as shown in  FIG. 2 , the energy source  2  and heater  3  can be aligned along the central longitudinal axis of the housing  7  in a substantially end-to-end arrangement so that an end face of the energy source  2  substantially faces an end face of the heater  3 . The mouthpiece  6  may be located at the second end  9  of the housing  7 , adjacent the heating chamber  4  and smokeable material  5 . 
     The length of the housing  7  may be approximately 130 mm. An example length of the energy source  2  is approximately 59 mm. The length of the heater  3  and heating region  4  may be approximately 50 mm. The depth, for example the diameter, of the heating chamber  4  may be between approximately 5 mm and approximately 15 mm, such as between approximately 8 mm and approximately 10 mm. The diameter of the energy source  2  may be between approximately 10.0 mm and approximately 15.0 mm, such as 14.6 mm. The diameter of the housing  7  may be between approximately 11 mm and approximately 18 mm. For example, the diameter of the housing&#39;s first end  8  may be 18 mm whilst the diameter of the mouthpiece  6  at the housing&#39;s second end  9  may be 15 mm. Dimensions other than those given above could alternatively be used. 
     The housing  7  is suitable for being gripped by a user during use of the apparatus  1  so that the user can inhale volatilized smokeable material compounds from the mouthpiece  6  of the apparatus  1 . 
     Heat insulation may be provided between the energy source  2  and the heater  3  to prevent direct transfer of heat from one to the other. 
     The heater  3  may comprise a printed heater  3 . For example, the heater  3  may comprise a substrate  3   a  and one or more heating elements  3   b  which may be printed onto or into the substrate  3   a.  As described below, the heating elements  3   b  may be configured to heat the substrate  3   a  at a rapid rate so that the temperature of the substrate  3   a  substantially matches the temperature of the heating elements  3   b  during heating of the smokeable material  5 . 
     The substrate  3   a  may comprise a ceramics material, such as Aluminum Nitride Ceramic, and the heating elements  3   b  may comprise electrically resistive trace elements  3   b  which are heated by electrical currents flowing in the elements  3   b.  For example, the heating elements  3   b  may comprise an electrically resistive metal such as Tungsten. The currents in the heating elements  3   b  may be caused by an electromotive force supplied by the energy source  2 , which is electrically coupled to the heater  3 . 
     The heating elements  3   b  are arranged in or on the substrate material  3   a  so as to heat the substrate  3   a.  As mentioned above, the arrangement of the heating elements  3   b  in or on the substrate  3   a  may be so as to heat the substrate  3   a  to approximately the same temperature as the heating elements  3   b.    
     The substrate  3   a  may be heated by the heating elements  3   b  to a volatilizing temperature of the smokeable material  5  so that heat from the heated substrate  3   a  causes components of the smokeable material  5  to be volatilized for inhalation through the mouthpiece  6 . Therefore, smokeable material  5  in the heating region  4  may be heated by both the heating elements  3   b  and the heated substrate  3   a.  The rate at which the temperature of the substrate  3   a  increases during heating may be substantially the same as the rate at which the temperature of the heating elements  3   b  increase. Therefore, the temperature of the heating elements  3   b  and the substrate  3   a  may be approximately equal during heating of the smokeable material  5 . 
     The arrangement of the heater  3  may be such that the peripheral surfaces of the heater  3  principally comprise those of the heated substrate  3   a  and, as such, the smokeable material  5  may be heated principally by heat emitted from the heated substrate  3   a  rather than being heated directly by the heating elements  3   b.  For example, as described below and shown schematically in  FIG. 1 , the heating elements  3   b  may be located principally or entirely inside the substrate  3   a  and may comprise a plurality of distinct heating layers of heating elements  3   b  separated by layers of substrate  3   a.    
     The coefficient of thermal expansion of the heating elements  3   b  may be matched to the coefficient of thermal expansion of the substrate  3   a.  In particular, the value of the coefficient of thermal expansion of the heating elements  3   b  may be substantially equal to the value of the coefficient of thermal expansion of the substrate  3   a.  The heating elements  3   b  and substrate  3   a  may therefore together form an expansion-matching heater structure  3 . 
     The matched thermal expansion coefficients of the substrate  3   a  and heating elements  3   b  means that thermal expansion of the heating elements  3   b  is matched by a corresponding expansion in the substrate  3   a.  Similarly, thermal contraction of the heating elements  3   b  is matched by a corresponding contraction in the substrate  3   a.  The expansion-matched nature of structure means that the heater  3  as a whole expands/contracts at substantially the same rate and by the same amount across the entire heater structure during heating/cooling. The expansion and contraction stresses on the heater structure  3  are small and the heater can be caused to undergo rapid, significant and frequent temperature transitions without placing significant material stress on the heater structure  3 . 
     The substrate  3   a  and the heating elements  3   b  may be chemically bonded together in the heater structure  3 . For example, the chemical bonds between the substrate  3   a  and the heating elements  3   b  may be formed during a sintering process, in which the substrate  3   a  and the heating elements  3   b  are fused together under the application of heat to create a solid heater structure  3 . 
     More specifically, the chemically bonded heater structure  3  may be manufactured by initially applying liquid heating element material  3   b  to one or more surfaces of the substrate material  3   a,  layering the substrate material  3   a  with the heating element material  3   b  and sintering the layered assembly to form the bonded heater structure  3 . This is illustrated schematically in  FIG. 1 . 
     Application of the liquid heating element material  3   b  can, for example, be carried out by printing the liquid material  3   b  onto the substrate material  3   a.  The application of the liquid heating element  3   b  onto the substrate  3   a  may be extremely precise so as to achieve very low tolerances, for example in the order of micrometres or nanometres, in the location of the heating element material  3   b  on the substrate  3   a  and thereby cause the heating elements  3   b  to form in very specific desired regions of the substrate  3   a.  A suitable printing process is to use a screen printer to print the liquid  3   b,  which may be in the form of an ink, onto the substrate material  3   a.    
     The substrate material  3   a  may comprise suitable binders and/or plasticizers which aid with the formation of the layered heater structure  3  before the formation of chemical bonds during sintering. Additionally or alternatively, the liquid heating element material  3   b  may comprise suitable binders and/or plasticizers. These may be of the same composition as the binders and/or plasticizers comprised in the substrate material  3   a.    
     The substrate material  3   a  onto which the heating element material  3   b  is applied may comprise pre-sintered layers of substrate  3   a,  such as pre-sintered sections of ceramic tape, which are built up on top of one another to form a layered structure comprising both the substrate  3   a  and the heating element material  3   b.  One or more vias may be formed in the layers of substrate material  3   a  so that the liquid heating material  3   b  fills the vias and, ultimately, forms interconnections between the layers of heating elements  3   b  in the heater  3 . 
     In particular, each layer of heating elements  3   b  may be interconnected to one or more other distinct layers of heating elements  3   b  by sections of heating element  3   b  which pass through the vias in the substrate  3   a.    
     The vias may be formed by any suitable process. For example, the vias may be formed by punching holes in the individual layers of substrate  3   a  before the layers of substrate  3   a  are layered on top of one another in the heater structure  3 . The holes in the layers of substrate  3   a  may be aligned in the layered structure so that interconnections between a plurality of layers of heating elements  3   b  are created during sintering. The vias formed between the layers  3   b  may be of any suitable shape, including three-dimensional shapes. 
     If desired, a plurality of electrical circuits can be printed onto the substrate  3   a  in order to provide control signals or measurement signals to/ from a controller  12  of the apparatus  1 . For example, temperature measurement circuits, which may incorporate one or more Resistance Temperature Detectors (RTD), can be printed onto, adjacent or underneath the heater elements  3   b,  or elsewhere on the substrate  3   a,  so that the temperature of the heater  3  can be monitored and adjusted by the controller  12  to obtain desired volatilizing or pre-volatilizing temperatures in the smokeable material  5 . 
     Before the assembly of substrate layers  3   a  and heating element material  3   b  is sintered to create the chemical bonds and cohesive nature of the heater  3  referred to above, the assembly may be de-bound of the binders and/or plasticizers referred to previously. 
     The chemical bonds and the matched thermal expansion coefficients create a robust heater structure  3 , which can be repeatedly re-used to heat and volatilize newly-loaded smokeable material  5  in the heating region  4 . 
     The heater  3  can be manufactured into any suitable shape using the layering technique described above. For example, the heater  3  may comprise a substantially hollow cylinder located around the smokeable material heating region  4  so that heat is emitted by the heater  3  in a radially inward direction. An example of this is described below in relation to  FIG. 2 . Alternatively, the smokeable material heating region  4  may be located around the heater  3 . An example is a co-axial arrangement in which the heater  3  emits heat in a radially outward direction into the heating region  4 , although other shapes are also possible as will be evident from the discussion below. 
     A specific example of an expansion matched, chemically bonded heater structure  3  is one in which the heating substrate  3   a  comprises pre-sintered Aluminum Nitride Ceramic tape and the heating element material  3   b  comprises Tungsten-containing ink which is screen printed onto the ceramics tape  3   a.  Once the ceramics tape  3   a  has been printed with the heating element material  3   b  and holes have been created to form the vias referred to above, the ceramics tape  3   a  is layered so as to form a structure containing internal layers of heating element material  3   b  connected together by vias in the tape  3   a.  The assembly is then sintered to form a cohesive and chemically-bonded heater  3 . During activation of the heater  3 , the Aluminum Nitride substrate  3   a  and Tungsten heating elements  3   b  expand and contract at a rate of approximately 4.5 parts per million per degree centigrade and thus the heater structure  3  as a whole expands and contracts without placing stress on any particular part of the structure  3 . 
     The thickness of the heater  3  may be small, such as less than 2 mm or less than 1 mm, which can contribute towards reducing the overall dimensions of the apparatus  1  compared to the use of other types of heaters. For example, the heater  3  may have a thickness of between approximately 0.1 mm and 2.0 mm, such as between approximately 0.3 mm and approximately 1.0 mm, although heaters  3  with larger thicknesses such as those up to 6.5 mm are equally possible. 
     The heater  3  can be operated over a wide range of power outputs in order to heat and maintain the smokeable material  5  in a desired temperature range. For example, the power output of the heater  3  may be in the range of zero to approximately  2000  watts/in t  and may be controllable by the controller  12  of the apparatus  1  so that the temperature of the smokeable material  5  is maintained or adjusted into the desired temperature range. The controller  12  may adjust the power output of the heater  3  based on measurements of temperature inside the heater  3 , at the peripheral surfaces of the heater  3  and/or inside the smokeable material  5 , using the temperature measurement circuits referred to above. 
     The controller  12  may cause the heater  3 , or distinct regions  10  of the heater  3 , to cycle between predetermined set temperatures for predetermined periods of time or may vary the temperature of the heater  3  and/or separate regions  10  of the heater  3  in accordance with a heating regime. The controller  12  and examples of suitable heating regimes are described in more detail below. The heater  3  has a low mass and therefore its use can help to reduce the overall mass of the apparatus  1 . 
     As shown in  FIG. 2  and referred to briefly above, the heater  3  may comprise a plurality of individual heating regions  10 . The heating regions  10  may be operable independently of one another so that different regions  10  can be activated at different times to heat the smokeable material  5 . This may be achieved by activating heating elements  3   b  located in particular regions  10  of the heater  3  at different times. The heating regions  10  may be arranged in the heater  3  in any geometric arrangement. However, in the example shown in  FIG. 2 , the heating regions  10  are geometrically arranged in the heater  3  so that different ones of the heating regions  10  are arranged to predominately and independently heat different regions of the smokeable material  5 . 
     For example, referring to  FIG. 2 , the heater  3  may comprise a plurality of axially aligned heating regions  10  in a substantially elongate arrangement. The regions  10  may each comprise an individual section of the heater  3 , such as an independently temperature-controllable section of the bonded substrate  3   a  and heating elements  3   b  structure  3  described above. The heating regions  10  may, for example, all be aligned with each other along a longitudinal axis of the heater  3 , thus providing a plurality of independent heating zones along the length of the heater  3 . 
     Referring to  FIG. 2 , each heating region  10  may comprise a hollow heating cylinder  10 , which may be a ring  10 , having a finite length which is significantly less than the length of the heater  3  as a whole. The arrangement of axially aligned heating regions  10  define the exterior of the heating chamber  4  and are configured to heat smokeable material  5  located in the heating chamber  4 . As mentioned previously, the heat is applied inwardly, predominately towards the central longitudinal axis of the heating chamber  4 . The heating regions  10  are arranged with their radial, or otherwise transverse, surfaces facing one another along the length of the heater  3 . The transverse surfaces of each heating region  10  may optionally be separated from the transverse surfaces of their neighboring heating region(s)  10  by thermal insulation  18 , as shown in  FIG. 2  and described below, or may connected and/or contiguous with their neighboring heating region(s)  10 . 
     As shown in  FIGS. 2 and 3 , the heater  3  may alternatively be located in a central region of the housing  7  and the heating chamber  4  and smokeable material  5  may be located around the longitudinal surface of the heater  3 . In this arrangement, thermal energy emitted by the heater  3  travels outwards from the longitudinal surface of the heater  3  into the heating chamber  4  and the smokeable material  5 . 
     The heating regions  10  may each comprise an individual section of the heater  3 . As shown in  FIGS. 1 to 4 , each heating region  10  may comprise a heating cylinder  10  having a finite length which is significantly less than the length of the heater  3  as a whole. However, other configurations of heater  3  could alternatively be used and so the use of cylindrical sections of heater  3  is not required. The heating regions  10  may be arranged with their transverse surfaces facing one another along the length of the heater  3 . The transverse surfaces of each region  10  may touch the transverse surfaces of its neighboring regions  10 . Alternatively, a heat insulating or heat reflecting layer may be present between the transverse surfaces of the regions  10  so that thermal energy emitted from each one of the regions  10  does not substantially heat the neighboring regions  10  and instead travels predominately into the heating chamber  4  and smokeable material  5 . Each heating region  10  may have substantially the same dimensions as the other regions  10 . 
     In this way, when a particular one of the heating regions  10  is activated, it supplies thermal energy to the smokeable material  5  located adjacent, for example radially adjacent, the heating region  10  without substantially heating the remainder of the smokeable material  5 . Referring to  FIG. 3 , the heated region of smokeable material  5  may comprise a ring of smokeable material  5  located around the heating region  10  which has been activated. The smokeable material  5  can therefore be heated in independent sections, for example rings or substantially solid cylinders, where each section corresponds to smokeable material  5  located directly adjacent a particular one of the heating regions  10  and has a mass and volume which is significantly less than the body of smokeable material  5  as a whole. 
     Additionally or alternatively, the heater  3  may comprise a plurality of elongate, longitudinally extending heating regions  10  positioned at different locations around the central longitudinal axis of the heater  3 . The heating regions  10  may be of different lengths, or may be of substantially the same length so that each extends along substantially the whole length of the heater  3 . 
     The heated sections of smokeable material  5  may comprise longitudinal sections of smokeable material  5  which lie parallel and directly adjacent to the longitudinal heating regions  10 . Therefore, as explained previously, the smokeable material  5  can be heated in independent sections. 
     As will be described further below, the heating regions  10  can each be individually and selectively activated. 
     The smokeable material  5  may be comprised in a cartridge  11  which can be inserted into the heating chamber  4 . For example, as shown in  FIG. 2 , the cartridge  11  can comprise a substantially solid body of smokeable material  5  such as a cylinder which fits into a recess of the heater  3 . In this configuration, the external surface of the smokeable material body faces the heater  3 . Alternatively, as shown in  FIG. 3 , the cartridge  11  can comprise a smokeable material tube  11  which can be inserted around the heater  3  so that the internal surface of the smokeable material tube  11  faces the longitudinal surface of the heater  3 . The smokeable material tube  11  may be hollow. The diameter of the hollow centre of the tube  11  may be substantially equal to, or slightly larger than, the diameter or otherwise transverse dimension of the heater  3  so that the tube  11  is a close fit around the heater  3 . The length of the cartridge  11  may be approximately equal to the length of the heater  3  so that the heater  3  can heat the cartridge  11  along its whole length. 
     The housing  7  of the apparatus  1  may comprise an opening through which the cartridge  11  can be inserted into the heating chamber  4 . The opening may, for example, comprise an opening located at the housing&#39;s second end  9  so that the cartridge  11  can be slid into the opening and pushed directly into the heating chamber  4 . The opening is preferably closed during use of the apparatus  1  to heat the smokeable material  5 . Alternatively, a section of the housing  7  at the second end  9  is removable from the apparatus  1  so that the smokeable material  5  can be inserted into the heating chamber  4 . The apparatus  1  may optionally be equipped with a user-operable smokeable material ejection unit, such as an internal mechanism configured to slide used smokeable material  5  off and/or away from the heater  3 . The used smokeable material  5  may, for example, be pushed back through the opening in the housing  7 . A new cartridge  11  can then be inserted as required. 
     As mentioned previously, the apparatus  1  may comprise a controller  12 , such as a microcontroller  12 , which is configured to control operation of the apparatus  1 . The controller  12  is electronically connected to the other components of the apparatus  1  such as the energy source  2  and heater  3  so that it can control their operation by sending and receiving signals. The controller  12  is, in particular, configured to control activation of the heater  3  to heat the smokeable material  5 . For example, the controller  12  may be configured to activate the heater  3 , which may comprise selectively activating one or more heating regions  10 , in response to a user drawing on the mouthpiece  6  of the apparatus  1 . In this regard, the controller  12  may be in communication with a puff sensor  13  via a suitable communicative coupling. The puff sensor  13  is configured to detect when a puff occurs at the mouthpiece  6  and, in response, is configured to send a signal to the controller  12  indicative of the puff An electronic signal may be used. The controller  12  may respond to the signal from the puff sensor  13  by activating the heater  3  and thereby heating the smokeable material  5 . The use of a puff sensor  13  to activate the heater  3  is not, however, essential and other means for providing a stimulus to activate the heater  3  can alternatively be used. For example, the controller  12  may activate the heater  3  in response to another type of activation stimulus such as actuation of a user-operable actuator. The volatilized compounds released during heating can then be inhaled by the user through the mouthpiece  6 . The controller  12  can be located at any suitable position within the housing  7 . An example position is between the energy source  2  and the heater  3 /heating chamber  4 , as illustrated in  FIG. 5 . 
     If the heater  3  comprises two or more heating regions  10  as described above, the controller  12  may be configured to activate the heating regions  10  in a predetermined order or pattern. For example, the controller  12  may be configured to activate the heating regions  10  sequentially along or around the heating chamber  4 . Each activation of a heating region  10  may be in response to detection of a puff by the puff sensor  13  or may be triggered in an alternative way, as described further below. 
     Referring to  FIG. 6 , an example heating method may comprise a first step Si in which an activation stimulus such as a first puff is detected followed by a second step S 2  in which a first section of smokeable material  5  is heated in response to the first puff or other activation stimulus. In a third step S 3 , hermetically sealable inlet and outlet valves  24  may be opened to allow air to be drawn through the heating chamber  4  and out of the apparatus  1  through the mouthpiece  6 . In a fourth step S 4 , the valves  24  are closed. These valves  24  are described in more detail below with respect to  FIG. 30 . In fifth S 5 , sixth S 6 , seventh S 7  and eighth S 8  steps, a second section of smokeable material  5  may be heated in response to a second activation stimulus such as a second puff, with a corresponding opening and closing of the heating chamber inlet and outlet valves  24 . In ninth S 9 , tenth S 10 , eleventh S 11  and twelfth S 12  steps, a third section of the smokeable material  5  may be heated in response to a third activation stimulus such as a third puff with a corresponding opening and closing of the heating chamber inlet and outlet valves  24 , and so on. As referred to above, means other than a puff sensor  13  could alternatively be used. For example, a user of the apparatus  1  may actuate a control switch to indicate that he/she is taking a new puff. In this way, a fresh section of smokeable material  5  may be heated to volatilize nicotine and aromatic compounds for each new puff. The number of heating regions  10  and/or independently heatable sections of smokeable material  5  may correspond to the number of puffs for which the cartridge  11  is intended to be used. Alternatively, each independently heatable smokeable material section  5  may be heated by its corresponding heating region(s)  10  for a plurality of puffs such as two, three or four puffs, so that a fresh section of smokeable material  5  is heated only after a plurality of puffs have been taken whilst heating the previous smokeable material section. Instead of activating each heating region  10  in response to an individual puff, the heating regions  10  may alternatively be activated sequentially, one after the other, in response to a single, initial puff at the mouthpiece  6 . For example, the heating regions  10  may be activated at regular, predetermined intervals over the expected inhalation period for a particular smokeable material cartridge  11 . The inhalation period may, for example, be between approximately one and approximately four minutes. Therefore, at least the fifth and ninth steps S 5 , S 9  shown in  FIG. 6  are optional. Each heating region  10  may be activated for a predetermined period corresponding to the duration of the single or plurality of puffs for which the corresponding independently heatable smokeable material section  5  is intended to be heated. Once all of the heating regions  10  have been activated for a particular cartridge  11 , the controller  12  may be configured to indicate to the user that the cartridge  11  should be changed. The controller  12  may, for example, activate an indicator light at the external surface of the housing  7 . 
     It will be appreciated that activating individual heating regions  10  in order rather than activating the entire heater  3  means that the energy required to heat the smokeable material  5  is reduced over what would be required if the heater  3  were activated fully over the entire inhalation period of a cartridge  11 . Therefore, the maximum required power output of the energy source  2  is also reduced. This means that a smaller and/or lighter energy source  2  can be installed in the apparatus  1 . 
     The controller  12  may be configured to de-activate the heater  3 , or reduce the power being supplied to the heater  3 , in between puffs. This saves energy and extends the life of the energy source  2 . For example, upon the apparatus  1  being switched on by a user or in response to some other stimulus, such as detection of a user placing their mouth against the mouthpiece  6 , the controller  12  may be configured to cause the heater  3 , or next heating region  10  to be used to heat the smokeable material  5 , to be partially activated so that it heats up in preparation to volatilize components of the smokeable material  5 . The partial activation does not heat the smokeable material  5  to a sufficient temperature to volatilize nicotine. A suitable temperature could be less than 120° C., such as approximately 100° C. In response to detection of a puff by the puff sensor  13 , the controller  12  can then cause the heater  3  or heating region  10  in question to heat the smokeable material  5  further in order to rapidly volatilize the nicotine and other aromatic compounds for inhalation by the user. If the smokeable material  5  comprises tobacco, a suitable temperature for volatilizing the nicotine and other aromatic compounds may be above 120° C., such between 150° C. and 250° C. or between 130° C. and 180° C. Therefore, examples of full activation temperatures include 180° C. and 250° C. A super-capacitor can optionally be used to provide the peak current used to heat the smokeable material  5  to the volatilization temperature. An example of a suitable heating pattern is shown in  FIG. 8 , in which the peaks may respectively represent the full activation of different heating regions  10 . As can be seen, the smokeable material  5  is maintained at the volatilization temperature for the approximate period of the puff which, in this example, is two seconds. 
     Three example operational modes of the heater  3  are described below. 
     In a first operational mode, during full activation of a particular heating region  10 , all other heating regions  10  of the heater are deactivated. Therefore, when a new heating region  10  is activated, the previous heating region is deactivated. Power is supplied only to the activated region  10 . 
     Alternatively, in a second operational mode, during full activation of a particular heating region  10 , one or more of the other heating regions  10  may be partially activated. Partial activation of the one or more other heating regions  10  may comprise heating the other heating region(s)  10  to a temperature which is sufficient to substantially prevent condensation of components such as nicotine volatilized from the smokeable material  5  in the heating chamber  4 . The temperature of the heating regions  10  which are partially activated is less than the temperature of the heating region  10  which is fully activated. The smokeable material  10  located adjacent the partially activated regions  10  is not heated to a temperature sufficient to volatilize components of the smokeable material  5 . 
     Alternatively, in a third operational mode, once a particular heating region  10  has been activated, it remains fully activated until the heater  3  is switched off Therefore, the power supplied to the heater  3  incrementally increases as more of the heating regions  10  are activated during inhalation from the cartridge  11 . As with the second mode previously described, the continuing activation of the heating regions  10  substantially prevent condensation of components such as nicotine volatilized from the smokeable material  5  in the heating chamber  4 . 
     The apparatus  1  may comprise a heat shield  100 , which is located between the heater  3  and the heating chamber  4 /smokeable material  5 . The heat shield  100  is configured to substantially prevent thermal energy from flowing through the heat shield  100  and therefore can be used to selectively prevent the smokeable material  5  from being heated even when the heater  3  is activated and emitting thermal energy. Referring to  FIG. 15 , the heat shield  100  may, for example, comprise a cylindrical layer of heat reflective material which is located co-axially around the heater  3 . Alternatively, if the heater  3  is located around the heating chamber  4  and smokeable material  5  as previously described with reference to  FIG. 2 , the heat shield  100  may comprise a cylindrical layer of heat reflective material which is located co-axially around the heating chamber  4  and co-axially inside of the heater  3 . The heat shield  100  may additionally or alternatively comprise a heat-insulating layer configured to insulate the heater  3  from the smokeable material  5 . 
     The heat shield  100  comprises a substantially heat-transparent window  101  which allows thermal energy to propagate through the window  101  and into the heating chamber  4  and smokeable material  5 . Therefore, the section of smokeable material  5  which is aligned with the window  101  is heated whilst the remainder of the smokeable material  5  is not. The heat shield  100  and window  101  may be rotatable or otherwise moveable with respect the smokeable material  5  so that different sections of the smokeable material  5  can be selectively and individually heated by rotating or moving the heat shield  100  and window  101 . The effect is similar to the effect provided by selectively and individually activating the heating regions  10  referred to above. For example, the heat shield  100  and window  101  may be rotated or otherwise moved incrementally in response to a signal from the puff detector  13 . Additionally or alternatively, the heat shield  100  and window  101  may be rotated or otherwise moved incrementally in response to a predetermined heating period having elapsed. Movement or rotation of the heat shield  100  and window  101  may be controlled by electronic signals from the controller  12 . The relative rotation or other movement of the heat shield  100 /window  101  and smokeable material  5  may be driven by a stepper motor  3   c  under the control of the controller  12 . This is illustrated in  FIG. 15 . Alternatively, the heat shield  100  and window  101  may be manually rotated using a user control such as an actuator on the housing  7 . The heat shield  100  does not need to be cylindrical and may optionally comprise one or more suitably positioned longitudinally extending elements and or/plates. 
     It will be appreciated that a similar result can be obtained by rotating or moving the smokeable material  5  relative to the heater  3 , heat shield  100  and window  101 . For example, the heating chamber  4  may be rotatable around the heater  3 . If this is the case, the above description relating to movement of the heat shield  100  can be applied instead to movement of the heating chamber  4  relative to the heat shield  100 . 
     The heat shield  100  may comprise a coating on the longitudinal surface of the heater  3 . In this case, an area of the heater&#39;s surface is left uncoated to form the heat-transparent window  101 . The heater  3  can be rotated or otherwise moved, for example under the control of the controller  12  or user controls, to cause different sections of the smokeable material  5  to be heated. Alternatively, the heat shield  100  and window  101  may comprise a separate shield  3   a  which is rotatable or otherwise moveable relative to both the heater  3  and the smokeable material  5  under the control of the controller  12  or other user controls. 
     The apparatus  1  may comprise air inlets  14  which allow external air to be drawn into the housing  7  and through the heated smokeable material  5  during puffing. The air inlets  14  may comprise apertures  14  in the housing  7  and may be located upstream from the smokeable material  5  and heating chamber  4  towards the first end  8  of the housing  7 . This is shown in  FIG. 2 . Another example is shown in  FIG. 7 . Air drawn in through the inlets  14  travels through the heated smokeable material  5  and therein is enriched with smokeable material vapors, such as aroma vapors, before being inhaled by the user at the mouthpiece  6 . Optionally, as shown in  FIG. 7 , the apparatus  1  may comprise a heat exchanger  15  configured to warm the air before it enters the smokeable material  5  and/or to cool the air before it is drawn through the mouthpiece  6 . For example, the heat exchanger  15  may be configured to use heat extracted from the air entering the mouthpiece  6  to warm new air before it enters the smokeable material  5 . 
     The apparatus  1  may comprise a smokeable material compressor  16  configured to cause the smokeable material  5  to compress upon activation of the compressor  16 . The apparatus  1  can also comprise a smokeable material expander  17  configured to cause the smokeable material  5  to expand upon activation of the expander  17 . The compressor  16  and expander  17  may, in practice, be implemented as the same unit as will be explained below. 
     The smokeable material compressor  16  and expander  17  may optionally operate under the control of the controller  12 . In this case, the controller  12  is configured to send a signal, such as an electrical signal, to the compressor  16  or expander  17  which causes the compressor  16  or expander  17  to respectively compress or expand the smokeable material  5 . Alternatively, the compressor  16  and expander  17  may be actuated by a user of the apparatus  1  using a manual control on the housing  7  to compress or expand the smokeable material  5  as required. 
     The compressor  16  is principally configured to compress the smokeable material  5  and thereby increase its density during heating. Compression of the smokeable material increases the thermal conductivity of the body of smokeable material  5  and therefore provides a more rapid heating and consequent rapid volatilization of nicotine and other aromatic compounds. This allows the nicotine and aromatics to be inhaled by the user without substantial delay in response to detection of a puff Therefore, the controller  12  may activate the compressor  16  to compress the smokeable material  5  for a predetermined heating period, for example one second, in response to detection of a puff. The compressor  16  may be configured to reduce its compression of the smokeable material  5 , for example under the control of the controller  12 , after the predetermined heating period. Alternatively, the compression may be reduced or automatically ended in response to the smokeable material  5  reaching a predetermined threshold temperature. A suitable threshold temperature may be in the range of approximately 120° C. to 250° C., or one of the other ranges discussed previously, and may be user selectable. A temperature sensor may be used to detect the temperature of the smokeable material  5 . 
     The expander  17  is principally configured to expand the smokeable material  5  and thereby decrease its density during puffing. The arrangement of smokeable material  5  in the heating chamber  4  becomes more loose when the smokeable material  5  has been expanded and this aids the gaseous flow, for example air from the inlets  14 , through the smokeable material  5 . The air is therefore more able to carry the volatilized nicotine and aromatics to the mouthpiece  6  for inhalation. The controller  12  may activate the expander  17  to expand the smokeable material  5  immediately following the compression period referred to above so that air can be drawn more freely through the smokeable material  5 . Actuation of the expander  17  may be accompanied by a user-audible sound or other indication to indicate to the user that the smokeable material  5  has been heated and that puffing can commence. 
     Referring to  FIGS. 8 and 9 , the compressor  16  and expander  17  may comprise a spring-actuated driving rod which is configured to compress the smokeable material  5  in the heating chamber  4  when the spring is released from compression. This is schematically illustrated in  FIGS. 8 and 9 , although it will be appreciated that other implementations could be used. For example, the compressor  16  may comprise a ring, having a thickness approximately equal to the tubular-shaped heating chamber  4  described above, which is driven by a spring or other means into the heating chamber  4  to compress the smokeable material  5 . Alternatively, the compressor  16  may be comprised as part of the heater  3  so that the heater  3  itself is configured to compress and expand the smokeable material  5  under the control of the controller  12 . A method of compressing and expanding the smokeable material  5  is shown in  FIG. 11 . The method comprises a first step P 1  of compressing the smokeable material  5  in its heating chamber  4 , a second step P 2  of heating the compressed smokeable material  5 , a third step P 3  of detecting a threshold temperature in the smokeable material  5 , a fourth step S 4  of expanding the smokeable material  5 , for example by releasing the compression force, and a fifth step S 5  of allowing external air to enter the smokeable material heating chamber  4 , for example by opening hermetically sealable inlet and outlet valves  24 . 
     The heater  3  may be integrated with the thermal insulation  18  mentioned previously. For example, referring to  FIG. 2 , the thermal insulation  18  may comprise a substantially elongate, hollow body, such as a substantially cylindrical tube of insulation  18 , which is located co-axially around the heating chamber  4  and into which the heating regions  10  are integrally located. The thermal insulation  18  may comprise a layer in which recesses are provided in the inwardly facing surface profile  21 . Heating regions  10  are located in these recesses so that the heating regions  10  face the smokeable material  5  in the heating chamber  4 . The surfaces of the heating regions  10  which face the heating chamber  4  may be flush with the inside surface  21  of the thermal insulation  18  in regions of the insulation  18  which are not recessed. 
     The integration of the heater  3  with the thermal insulation  18  means that the heating regions  10  are substantially surrounded by the insulation  18  on all sides of the heating regions  10  other than those which face inwardly towards the smokeable material heating chamber  4 . As such, heat emitted by the heater  3  is concentrated in the smokeable material  5  and does not dissipate into other parts of the apparatus  1  or into the atmosphere outside the housing  7 . 
     Integration of the heater  3  with the thermal insulation  18  may also reduce the thickness of the combination of heater  3  and thermal insulation  18 . This can allow the diameter of the apparatus  1 , in particular the external diameter of the housing  7 , to be further reduced. Alternatively, the reduction in thickness provided by the integration of the heater  3  with the thermal insulation  18  can allow a wider smokeable material heating chamber  4  to be accommodated in the apparatus  1 , or the introduction of further components, without any increase in the overall width of the housing  7 . 
     Alternatively, the heater  3  may be located adjacent the insulation  18  rather than being integrated into it. For example, if the heater  3  is located externally of the heating chamber  4  as shown in  FIG. 2 , the insulation  18  may be located around the outside of the heater  3  so that the inwardly-facing surface  21  of the insulation faces the heater  3 . If the heater  3  is located internally of the heating chamber  4 , the heater  3  may be located around the outwardly-facing surface  22  of the insulation  18 . 
     Optionally, a barrier may be present between the heater  3  and the insulation  18 . For example, a layer of stainless steel may be present between the heater  3  and the insulation  18 . The barrier may comprise a stainless steel tube which fits between the heater  3  and the insulation  18 . The thickness of the barrier may be small so as not to substantially increase the dimensions of the apparatus. An example thickness is between approximately 0.1 mm and 1.0 mm. 
     Additionally, a heat reflecting layer may be present between the transverse surfaces of the heating regions  10 . The arrangement of the heating regions  10  relative to each other may be such that thermal energy emitted from each one of the heating regions  10  does not substantially heat the neighboring heating regions  10  and instead travels predominately inwardly from the circumferential surface of the heating region  10  into the heating chamber  4  and smokeable material  5 . Each heating region  10  may have substantially the same dimensions as the other regions  10 . 
     The heater  3  may be bonded or otherwise secured in the apparatus  1  using pressure sensitive adhesive. For example, the heater  3  may be adhered to the insulation  18  or barrier referred to above using pressure sensitive adhesive. The heater  3  may alternatively be adhered to the cartridge  11  or an exterior surface of the smokeable material heating chamber  4 . 
     As an alternative to the use of pressure sensitive adhesive, the heater  3  may be secured in position in the apparatus  1  using self-fusing tape or by clamps which clamp the heater  3  in place. All of these methods provide a secure fixing for the heater  3  and allow effective heat transfer from the heater  3  to the smokeable material  5 . Other types of fixing are also possible. 
     The thermal insulation  18 , which is provided between the smokeable material  5  and an external surface  19  of the housing  7 , as described above, reduces heat loss from the apparatus  1  and therefore improves the efficiency with which the smokeable material  5  is heated. For example, referring to  FIG. 2 , a wall of the housing  7  may comprise a layer of insulation  18  which extends around the outside of the heating chamber  4 . The insulation layer  18  may comprise a substantially tubular length of insulation  18  located co-axially around the heating chamber  4  and smokeable material  5 . This is shown in  FIG. 2 . It will be appreciated that the insulation  18  could also be comprised as part of the smokeable material cartridge  11 , in which it would be located co-axially around the outside of the smokeable material  5 . 
     Referring to  FIG. 12 , the insulation  18  may comprise vacuum insulation  18 . For example, the insulation  18  may comprise a layer which is bounded by a wall material  19  such as a metallic material. An internal region or core  20  of the insulation  18  may comprise an open-cell porous material, for example comprising polymers, aerogels or other suitable material, which is evacuated to a low pressure. The pressure in the internal region  20  may be in the range of 0.1 to 0.001 mbar. The wall  19  of the insulation  18  is sufficiently strong to withstand the force exerted against it due to the pressure differential between the core  20  and external surfaces of the wall  19 , thereby preventing the insulation  18  from collapsing. The wall  19  may, for example, comprise a stainless steel wall  19  having a thickness of approximately 100 μm. The thermal conductivity of the insulation  18  may be in the range of 0.004 to 0.005 W/mK. The heat transfer coefficient of the insulation  18  may be between approximately 1.10 W/(m 2 K) and approximately 1.40 W/(m 2 K) within a temperature range of between approximately 150 degrees Celsius and approximately 250 degrees Celsius. The gaseous conductivity of the insulation  18  is negligible. A reflective coating may be applied to the internal surfaces of the wall material  19  to minimize heat losses due to radiation propagating through the insulation  18 . The coating may, for example, comprise an aluminum IR reflective coating having a thickness of between approximately 0.3 μm and 1.0 μm. The evacuated state of the internal core region  20  means that the insulation  18  functions even when the thickness of the core region  20  is very small. The insulating properties are substantially unaffected by its thickness. This helps to reduce the overall size of the apparatus  1 . 
     As shown in  FIG. 12 , the wall  19  may comprise an inwardly-facing section  21  and an outwardly-facing section  22 . The inwardly-facing section  21  substantially faces the smokeable material  5  and heating chamber  4 . The outwardly-facing section  22  substantially faces the exterior of the housing  7 . During operation of the apparatus  1 , the inwardly-facing section  21  may be warmer due to the thermal energy originating from the heater  3 , whilst the outwardly-facing section  22  is cooler due to the effect of the insulation  18 . The inwardly-facing section  21  and the outwardly-facing section  22  may, for example, comprise substantially parallel longitudinally-extending walls  19  which are at least as long as the heater  3 . The internal surface of the outwardly-facing wall section  22 , i.e. the surface facing the evacuated core region  20 , may comprise a coating for absorbing gas in the core  20 . A suitable coating is a titanium oxide film. 
     The thermal insulation  18  may comprise hyper-deep vacuum insulation such as an Insulon® Shaped-Vacuum Thermal Barrier as described in U.S. Pat. No. 7,374,063. The overall thickness of such insulation  18  may be extremely small. An example thickness is between approximately 1 mm and approximately 1 μm, such as approximately 0.1 mm, although other larger or smaller thicknesses are also possible. The thermally insulating properties of the insulation  18  are substantially unaffected by its thickness and therefore thin insulation  18  can be used without any substantial additional heat loss from the apparatus  1 . The very small thickness of the thermal insulation  18  may allow the size of the housing  7  and apparatus  1  as a whole to be reduced beyond the sizes previously discussed and may allow the thickness, for example the diameter, of the apparatus  1  to be approximately equal to smoking articles such as cigarettes, cigars and cigarillos. The weight of the apparatus  1  may also be reduced, providing similar benefits to the size reductions discussed above. 
     Although the thermal insulation  18  described previously may comprise a gas-absorbing material to maintain or aid with creation of the vacuum in the core region  20 , a gas absorbing material is not used in the deep-vacuum insulation  18 . The absence of the gas absorbing material aids with keeping the thickness of the insulation  18  very low and thus helps to reduce the overall size of the apparatus  1 . The geometry of the hyper-deep insulation  18  allows the vacuum in the insulation to be deeper than the vacuum used to extract molecules from the core region  20  of the insulation  18  during manufacture. For example, the deep vacuum inside the insulation  18  may be deeper than that of the vacuum-furnace chamber in which it is created. The vacuum inside the insulation  18  may, for example, be of the order 10 −7  Torr. Referring to  FIG. 17 , an end of the core region  20  of the deep-vacuum insulation  18  may taper as the outwardly facing section  22  and inwardly facing section  21  converge to an outlet  25  through which gas in the core region  20  may be evacuated to create a deep vacuum during manufacture of the insulation  18 .  FIG. 17  illustrates the outwardly facing section  22  converging towards the inwardly facing section  21  but a converse arrangement, in which the inwardly facing section  21  converges to the outwardly facing section  22 , could alternatively be used. The converging end of the insulating wall  19  is configured to guide gas molecules in the core region  20  out of the outlet  25  and thereby create a deep vacuum in the core  20 . The outlet  25  is sealable so as to maintain a deep vacuum in the core region  20  after the region  20  has been evacuated. The outlet  25  can be sealed, for example, by creating a brazed seal at the outlet  25  by heating brazing material at the outlet  25  after gas has been evacuated from the core  20 . Alternative sealing techniques could be used. 
     In order to evacuate the core region  20 , the insulation  18  may be placed in a low pressure, substantially evacuated environment such as a vacuum furnace chamber so that gas molecules in the core region  20  flow into the low pressure environment outside the insulation  18 . When the pressure inside the core region  20  becomes low, the tapered geometry of the core region  20 , and in particular the converging sections  21 ,  22  referred to above, becomes influential in guiding remaining gas molecules out the core  20  via the outlet  25 . Specifically, when the gas pressure in the core region  20  is low, the guiding effect of the converging inwardly and outwardly facing sections  21 ,  22  is effective to channel the remaining gas molecules inside the core  20  towards the outlet  25  and make the probability of gas exiting the core  20  higher than the probability of gas entering the core  20  from the external, low pressure environment. In this way, the geometry of the core  20  allows the pressure inside the core  20  to be reduced below the pressure of the environment outside the insulation  18 . 
     Optionally, as previously described, one or more low emissivity coatings may be present on the internal surfaces of the inwardly and outwardly facing sections  21 ,  22  of the wall  19  in order to substantially prevent heat losses by radiation. 
     Although the shape of the insulation  18  is generally described herein as substantially cylindrical or similar, the thermal insulation  18  could be another shape, for example in order to accommodate and insulate a different configuration of the apparatus  1  such as different shapes and sizes of heating chamber  4 , heater  3 , housing  7  or energy source  2 . For example, the size and shape of deep-vacuum insulation  18  such as an Insulon® Shaped-Vacuum Thermal Barrier referred to above is substantially unlimited by its manufacturing process. Suitable materials for forming the converging structure described above include ceramics, metals, metalloids and combinations of these. 
     Referring to the schematic illustration in  FIG. 13 , a thermal bridge  23  may connect the inwardly-facing wall section  21  to the outwardly-facing wall section  22  at one or more edges of the insulation  18  in order to completely encompass and contain the low pressure core  20 . The thermal bridge  23  may comprise a wall  19  formed of the same material as the inwardly and outwardly-facing sections  21 ,  22 . A suitable material is stainless steel, as previously discussed. The thermal bridge  23  has a greater thermal conductivity than the insulating core  20  and therefore may undesirably conduct heat out of the apparatus  1  and, in doing so, reduce the efficiency with which the smokeable material  5  is heated. 
     To reduce heat losses due to the thermal bridge  23 , the thermal bridge  23  may be extended to increase its resistance to heat flow from the inwardly-facing section  21  to the outwardly-facing section  22 . This is schematically illustrated in  FIG. 14 . For example, the thermal bridge  23  may follow an indirect path between the inwardly-facing section  21  of wall  19  and the outwardly-facing section  22  of wall  19 . This may be facilitated by providing the insulation  18  over a longitudinal distance which is longer than the lengths of the heater  3 , heating chamber  4  and smokeable material  5  so that the thermal bridge  23  can gradually extend from the inwardly-facing section  21  to the outwardly-facing section  22  along the indirect path, thereby reducing the thickness of the core  20  to zero, at a longitudinal location in the housing  7  where the heater  3 , heating chamber  4  and smokeable material  5  are not present. 
     Referring to  FIG. 16 , as previously discussed, the heating chamber  4  insulated by the insulation  18  may comprise inlet and outlet valves  24  which hermetically seal the heating chamber  4  when closed. The valves  24  can thereby prevent air from undesirably entering and exiting the chamber  4  and can prevent smokeable material flavors from exiting the chamber  4 . The inlet and outlet valves  24  may, for example, be provided in the insulation  18 . For example, between puffs, the valves  24  may be closed by the controller  12  so that all volatilized substances remain contained inside the chamber  4  in-between puffs. The partial pressure of the volatilized substances between puffs reaches the saturated vapour pressure and the amount of evaporated substances therefore depends only on the temperature in the heating chamber  4 . This helps to ensure that the delivery of volatilized nicotine and aromatic compounds remains constant from puff to puff. During puffing, the controller  12  is configured to open the valves  24  so that air can flow through the chamber  4  to carry volatilized smokeable material components to the mouthpiece  6 . A membrane can be located in the valves  24  to ensure that no oxygen enters the chamber  4 . The valves  24  may be breath-actuated so that the valves  24  open in response to detection of a puff at the mouthpiece  6 . 
     The valves  24  may close in response to a detection that a puff has ended. Alternatively, the valves  24  may close following the elapse of a predetermined period after their opening. The predetermined period may be timed by the controller  12 . Optionally, a mechanical or other suitable opening/closing means may be present so that the valves  24  open and close automatically. For example, the gaseous movement caused by a user puffing on the mouthpiece  6  may be used to open and close the valves  24 . Therefore, the use of the controller  12  is not necessarily required to actuate the valves  24 . 
     The mass of the smokeable material  5  which is heated by the heater  3 , for example by each heating region  10 , may be in the range of 0.2 to 1.0 g. The temperature to which the smokeable material  5  is heated may be user controllable, for example to any temperature within the temperature range of 120° C. to 250° C. as previously described. The mass of the apparatus  1  as a whole may be in the range of 70 to 125 g, although the mass of the apparatus  1  can be lower when incorporating the type of heater  3  described above and/or deep-vacuum insulation  18 . A battery  2  with a capacity of 1000 to 3000 mAh and voltage of 3.7V can be used. The heating regions  10  may be configured to individually and selectively heat between approximately  10  and  40  sections of smokeable material  5  for a single cartridge  11 . 
     It will be appreciated that any of the alternatives described above can be used singly or in combination. 
     In order to address various issues and advance the art, the entirety of this disclosure shows by way of illustration various embodiments in which the claimed invention(s) may be practiced and provide for superior apparatus. The advantages and features of the disclosure are of a representative sample of embodiments only, and are not exhaustive and/or exclusive. They are presented only to assist in understanding and teach the claimed features. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects of the disclosure are not to be considered limitations on the disclosure as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilized and modifications may be made without departing from the scope and/or spirit of the disclosure. Various embodiments may suitably comprise, consist of, or consist essentially of, various combinations of the disclosed elements, components, features, parts, steps, means, etc. In addition, the disclosure includes other inventions not presently claimed, but which may be claimed in future.